I'm bumping this only to help support my comment on AlexChejlyk's thread

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Ian Murray
http://www.TriathlonTrainingSeries.com
I like the pursuit of mastery
Twitter - @TriCoachIan

Hi Ian. I’m coming off a large Giant Trinity which I believe fitted me well. Any help you can give with sizing would be greatly appreciated.

Height: 188cm
Inseam: 88cm
Saddle Height: 820mm
Pad Stack: 690mm
Pad Reach: 420-430mm (back of the pads)

I’m looking at the PRSix 2 Disc. I’m uk based so it will be a frame set purchase followed by a self build. I pretty much have all the components except the bars, but I know a few erailers that stock the PD Aeria Ultimate. Any other base bars worth considering?

If you need any more detail please let me know.

Dean

Dean,
The frame size is a 54. And, if you use QRs stem and bar configuration then you need to do the "mid clamp" (there's a clam-shell in the bar clamp and mid means 1/2 on top of base bar and 1/2 below base bar). Then you need 60mm of pedestal. As to the cockpit length... you would use their 75mm stem with bracket rear word and the pads back.

If you want to build this bike with some other front end.... I don't have an immediate answer for you other than this.... This is a super bike (defined by me as a bike built with a proprietary, original equipment manufacture stem that hides all cables and hoses) so, use their stem. Also, you mentioned the Aeria Ultimate - that's the bar that is mated to this bike, it's also a super sexy set up so you would do well to stay with it. If you wanted to make it more interesting with some 51Speedshop extensions or something like that, that would be cool.

Now I need to expand my answer this this. You've got long legs for your height. The Pad Y is understandable at 690. I might have guessed 675 but that's pretty close and could pertain to cranks being too long (you should ride 165s at the longest and probably 160mm). If you did that your Pad Y would likely drop 10-20mm. Now, about that Pad X - that's SHORT, very short. I would have guessed 470 maybe 455 but 425 is crazy short. You are probably not riding - what we used to call "steep" enough in seat angle, but now think of as "on the nose of the saddle". 9 times out of 10 it's because of the saddle isn't comfortable enough to ride the nose or, perhaps, it's not forward enough on the rails. The point of this last paragraph is that you investigate altering you position to be a bit longer and quite a bit longer on the new bike - and what is needed to make that happen (shorter cranks, new position with saddle). And I bring all this up because the 54 can go lower and will go longer even with the spec'd 75mm stem in my notes here.

Ian

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Ian Murray
http://www.TriathlonTrainingSeries.com
I like the pursuit of mastery
Twitter - @TriCoachIan

Thanks for the response Ian. I will re-visit my co-ordinates against those numbers you suggest, setting up my Wattbike atom based on those figures. I will also be booking myself in for another bike fit just to be 100%.

Hi Ian, Considering a PRFive and would like your opinion on the size and any spacers, etc. you would recommend.

My measurements are:

Height - 171.5cm
Inseam - 750mm
Seat Height - 705mm
Pad Y - 660mm
Pad X - 432mm

Thanks!

Hi Ian,

I recently bought a 2nd hand 2019 Prsix in size 56, which was a bit of a gamble, but long story short my previous bike was stolen and I needed a race bike fast. I have had a fit, which fits me on the bike, but I am unsure whether I should persist with the size 56, or sell and move to a 54, which I believe would be better. I did check the QR website first and they advised I could pick either the 54 or the 56 (height 6ft). My main problem is that the seatpost seems extremely low and everything is set back more or less to the limits (bar, extensions, seat etc), and I am unsure whether it is too low or in a position feasible for the long term. Other than that I am sitting comfortably and have no issues when riding, and am able to generate race power no problem.

My retul measurements after the fitting are as follows -

Saddle height 737mm
Saddle Setback 3mm
Arm Pad Stack BB 666mm (I have since added another 40mm spacers to this)
Seat Tube Angle 80 degrees
Frame Stack 561mm
Frame Reach 436mm
Arm Pad Reach Saddle 544mm (I have since changed arm pads so this is effectively around 520mm)
Handlebar Stack 598mm
Handlebar Reach 547mm

Do you think it is worthwhile persisting with the 56, or would I be better selling and getting hold of a 54. I can probably get back what I paid so there is no financial penalty.

Thanks,
Ian

Ian,
Retul has some terms on their fit report that create confusion. I need Pad Y to prescribe (and to answer your questions) and you've given me exactly that: "Arm Pad Stack BB 666mm (you've added another 40mm since then). I also need Pad X and it's NOT "Arm Pad Reach Saddle 544mm" - it's probably something like "Arm Pad Reach BB". Now maybe.....what I'm about to do is dangerous...maybe it's 541. I'm guessing at that because the nose of the saddle is 3mm behind the BB ("setback 3mm) and if I subtract 3 from 544 = 541. MAYBE. I'd like to know for sure so get back to me here, but I'm still gonna riff on Pad Y of 706 and Pad X of 541.

So, as to the size 56 you have now....
If your Pad Y is 706 then you have one of three possible configurations:
1) The stem/bar clamp is in the low position (both clamshells on top of base bar) + 65mm of pedestal
2) The stem/bar clamp mid (one clamp on top, one on bottom) + 55mm of pedestal
3) The stem/bar clamp high (both on bottom) + 45mm of pedestal.

If I were building this bike I'd opt for #2 first and #3 second (I like less pedestal)

If your Pad X is 541 (if, mind you) then the two most realistic options are these:
1) you have a 90mm stem with the bracket forward and the arm rest hole rearward (result is 530mm)
2) you have the 110mm stem with the bracket forward and the arm rets hole rearward (result is 550mm)
It's important to note something here... #2 is the absolute longest this bike goes: 110mm stem + bracket going forward and arm rest dangling out front as far as possible. And #1 is nearly the longest this bike goes.

So your question is essentially.. should I sell the 56 and get a 54 'cause the post is low in the frame? My answer is if (this is the big "if") if your Pad X is really 541 then don't get a 54 because the longest Pad X you can get on that bike is a 540, that's your number and if you ever want to adjust out a hair you cannot. Also, max Pad Y on a 54 is 715, that's only 9mm higher than where you are now. Sure the post might be out of the frame a bit more but you are painted into a corner maxed out on the size 54.

So...I'd like to know 3 things:
1) What is the actual Pad Y you are currently riding?
2) What is the actual Pad X of what you are currently riding?
3) Do you like that position in terms of comfort, power, aero?

So, if you could get the bike on a level floor. Roll it up to a wall that is at a 90 degree angle to that floor so the front tire is touching the wall. Then line up the front wheel with the frame and measure & math out these two things:
1) measure from the floor up to the center of the bottom bracket (A). Measure from the floor up to the top of the arm pad (B). Subtract A form B and tell me Pad Y.
2) measure from the wall back to the back edge of the arm pad (A). Measure from the wall back to the bottom bracket (B). Subtract A from B and tell me Pad X.

Get back to me here and let's see what's really happening.

Ian

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Ian Murray
http://www.TriathlonTrainingSeries.com
I like the pursuit of mastery
Twitter - @TriCoachIan

Hi Ian,

Thanks in advance for offering fit advice! I'm deciding between the QR PRSix2, PRSix, and PRFive, especially with the 4th of July sale on. What size(s) do you recommend for the following measurements?

Saddle height: 750
Saddle setback: 70
Saddle to pad drop (top to top): 65
Saddle to pad: 470
Pad-X: 390
Pad-Y: 685
Pad spacing (center to center): 265
Extension length (center of pad to button): 32
Extension spacing: 65

Looking at these numbers compared with other posts on this thread, it seems like my saddle-to-pad-drop is quite small...? Should I be questioning these fit numbers?

Thanks,

Brett

Brett,
I do want to check in on a few things. Pad Y of 685 and Pad X of 390 - that's an odd pairing. Your Pads are pretty high for that X or the Cockpit is very short for the that Y. Let me ask you a couple of questions:

• Were these numbers given to you from a fitter as your fit coordinates? If so, may I see the fit sheet?
• Is this a road bike with clip on aerobars?
• What is the make & model of your saddle and... do you sit on the nose of that saddle or in the middle of it?
• Are you comfortable in aero on this bike..do you feel powerful?
• Lastly how tall are you and what's your inseam?

Let me know, we can work through this together.

Ian

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Ian Murray
http://www.TriathlonTrainingSeries.com
I like the pursuit of mastery
Twitter - @TriCoachIan

• Fit sheet attached. I had to follow up with the fitter to ask for the PadX and PadY numbers, and here's what he said:


• Normally I would have those data points from the report, but those numbers are off so I did not want to confuse you. That is correct, I made a new sheet so it would be legible and forgot to put the saddle measurement to pad. It is 470mm. Then you have to take the saddle setback and subtract it from that number so it gives you a pad X of 390mm. To get Y measurement for pad, you would subtract drop from saddle height. 750-65= 685
• Not a road bike -- I did a GURU fit for tri-bikes so that I could shop proper sizes.
• Saddle was an Adamo PR 1.0 (as noted on the fit sheet) -- I think I was fairly forward on it, but maybe not all the way...?
• I felt comfortable, felt reasonably powerful, but didn't really rip into it.
• Height: 5' 9"
• Inseam: 32" (crotch-to-floor)

Brett,

Based on your morphology I think your Pad Y should be around 613 (and we have it at 685) and your Pad X should be around 473 and we have it at 390. Those discrepancies are too great, but I like that you're comfortable and feeling powerful.

Let's try this - just to be more precise, cause sometimes us fitters make mistakes and sometimes things get moved after we record it, etc. Let's find out where you're really riding.

Put your bike on a level floor and roll it forward 'til the tire touches a wall (you might need someone to hold it up-right while you do this). Take these measurements for me:
1) measure from the floor up to the center of the bottom bracket. Prolly easiest to do this on the non-drive side, most cranks have a bolt center and you can go right to the middle of that. Let's call that "Ay". Then measure from the floor up to the top of the back of the pad (near where your elbow might rest). Let's call that "By". Now subtract the smaller number Ay from By and tell me your Pad Y.
2) make sure the front wheel is in line with the frame and measure from the wall back to the back of the pad (again, where your elbow might rest) - that's "Ax". Then measure from the wall back to the center of the bottom bracket - that's "Bx". Subtract Ay from By and tell me your Pad X

When you do this make sure the yard stick or measuring tape is straight up and down for the Y business and level for the X stuff.

Let me know, I'm eager to figure this out.

Ian

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Ian Murray
http://www.TriathlonTrainingSeries.com
I like the pursuit of mastery
Twitter - @TriCoachIan

Ian,

I can't take those measurements you requested because I don't have a tri-bike to measure them on. I'm in the market for one now :)

Should I call the fitter and ask for a double-check?

Thanks.

Brett,

Here's what I'd like you to do. Could you take 4 min and read this article. Look at the graph that Slowman made and plot Pad Y of 685 and Pad X of 390 in comparison of every other human in the "study". If we think those numbers are right (I don't) then there needs to be a really good, obvious reason why you're an major outlier. And I just don't think you are - you're 5'9" with a 32" inseam - unless your live everyday in some sort of back brace I don't why you're the outlier's outlier. I think you belong in the same position we all ride in.

As an exercise I'll proceed with what we've got. Take note of the "noise" in the way that we're arriving at the numbers - not the least of which is the accuracy of the math: "I made a new sheet so it would be legible and forgot to put the saddle measurement to pad. It is 470mm. Then you have to take the saddle setback and subtract it from that number so it gives you a pad X of 390mm...and... setback is 70" that right there should equal a Pad X of 400 and not 390 so, yeah, I worry about these numbers.

Here we go with all three bikes and two sets of numbers: 685/390 (where your fitter has you now) or 620/440 (where I would have guessed you'd ride).

PRfive... size 52 with a 70mm stem in the +17 position, 20mm of spacer under stem and pads back 1 hole shy of the max. That results in a Pad Y of 684/387. Now, same bike, same stem...size 52, 70mm but now in the -17 degree position with stem slammed, pads just one hole forward of center and you get 621/444. And you can get lots of positions in between to progress to perfection.

PRsix (and PRsix2)... and this is where your fit comes into question... you'd have to ride a size 50 to get the Pad X of 390. But the 50 maxes out at a Pad Y of 675. So, we look at a size 52 bike now you can get your 685 Pad Y (and just barely) but the shortest the 52 cockpit goes is 405.

Get back to me here. Let's figure this out.

Ian

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Ian Murray
http://www.TriathlonTrainingSeries.com
I like the pursuit of mastery
Twitter - @TriCoachIan

Hi-

Thanks in advance...

Seriously considering the PRfive with Di2 (but not disc, don't plan on stopping much, ha). My current (and first) tri bike is a 2009 Cervelo P2C 58 cm, that I bought used about 6-7 years ago. I've had a fitter eyeball me on the bike a couple of times and make some adjustments but never had an official Retul or similar fitting.

My stats:
Age: 48
Height: 183 cm (6 foot)
In seam: 83.5 cm (somewhere between 32 and 33 inches I think)
Pad X: 482 (I think? hard to measure accurately)
Pad Y: 724 (again, hard to measure)

My current fit on my p2c is...fine? Not "comfortable" but I can tolerate it. I've done a bunch of local races, one HIM, and one full IM on the bike without any significant problems. I really want a bike with electronic shifting, and I've done tri long enough that it's probably time to upgrade.

The QR sizing guide says 54 or 56 cm frame. Which one? And any additional tips re stems or what not?

Thanks again!

Alright Ian, went back to the fitter and did this over again, this time with hips much further forward than the last round.

Height: 5' 8"
Inseam: 32"
Saddle height: 754
Saddle setback: 24 (used to be 70)
Saddle nose to center pad: 460
Saddle to pad drop: 11
Crank length: 165

Measured the following:
Pad X (rear of pad): 385
Pad Y (top of pad): 590

Are these consistent with the numbers above? I did some quick calculations using the top numbers to estimate PadX-Y, and I get:
Pad X (saddle-nose-to-center-pad minus saddle-setback): 460 - 24 = 436. (note that this is to the pad's center)
Pad Y (saddle-height minus saddle-to-pad-drop): 754 - 11 = 743

What am I looking at for a PRSix?

Brett,
Well there's much more logic in here now. Set back of 24, drop of 11, sensible, logical - Yeah!

For a PRsix...it's a size 48* with 75mm stem, mid bar clamp with 20mm of pedestal, pad bracket rearward and pads back 100% yielding a Pad X of 375 or one hole forward of max-back yielding a Pad X of 390.

Your Pad Y is now (590) lower than what I expected oh so many posts ago 613 - that might be nice, you might need to come up a hair in the future. The bike prescribing will as low as 560 and has high as 655. It's nice to have that room to move.

Your Pad X is now (385). I expected it to be 473... it was at 390 when your set back was 70 and now it's 385 when the set back is 24... Hmmm!?!?! Doesn't matter and here's why: the bike I'm prescribing will meet you at 385, hell it'll even come on back to 375 but - and this is important to me 'cause I think you're gonna creep your cockpit farther and farther out past 450 - this bike, with the 75mm stem can go as far as 460.

*I put an asterisk on the 48 because some folks associate 48cm bike with ultra petite women who stand 4'1" tall. QR uses and incredibly smart way of sizing the bikes; by Stack. The frame stack of this bike is 480mm. Your Pad Y of 590 could happen on a 50 too but the Pad X wont so it's a 48.

Ian

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Ian Murray
http://www.TriathlonTrainingSeries.com
I like the pursuit of mastery
Twitter - @TriCoachIan

I also have no idea why the Pad-X would be shorter than before -- we started at last week's fit position and then moved the entire thing forward (saddle + pads) so I'm not sure how it could be shorter other than a possible measuring error last week vs. this week.


I found the QR charts the other day as well -- just one small question on this all: you say that a frame size 50 can't hit a Pad-X of 385, but I see "38.5" for the 75 mm stem, front armrest hole, rearward bracket. Am I misreading the chart somehow ("Gen2 PRSix 50cm fit coordinates")?

The main reason I ask is because a 50 gives me more room to go forward as you suggest, whereas it looks like the 48 would stop me short of that.

Brett,

You are reading it correctly. The 50 will come back to a 385mm for Pad X. The max Pad X on the 50 is just 10mm longer the the max Pad X on the 48. And this truth bares out over each stem option: 75mm stem max Pad X 460/470 (48x50). 90mm stem Pad X 475/485 (48/50). 110mm stem Pad X 495/505 (48/50). I mention this because it's nice to get the stem the first time but it's easy to acquire another stem anytime.

I cannot, for the life of me, figure out how you had a set back of 70 with Pad X of 390.....and then a refit where the seat moved forward 46mm to a new set back of 24 and that resulted in a Pad X that was 5mm shorter that before. It's unimaginable. If the 390 had been right then the saddle moving forward 46mm would result in a Pad X of 436 not 385. Remember I predicted a Pad X of 470ish so I never believed the 390 and I am now in a state of greater disbelief over this 385.

I think you only have two options. I'm going offer them both up and you can make your own choice.

OPTION ONE: Order a QR PRsix size 48 with a 90mm stem (this is a change from my previous script). If your Pad Y is 590 or 655 or somewhere between you can have it. You can have the 590 (new from fitter), you have 613 (my guess), you have have 655 (just 30mm off the 685 originally from fitter. I'm serious about this because you might start at 590 and it's good for 60,75,90min but by 2 hours the back of your neck and shoulders are screaming and you might want to come up 10-20mm and it'll do it. You might have this bike for 10 years and after 6 years you might want to come up another 20-30mm and it'll do it. .... AND....with that 90mm stem you can go as short Pad X 390 (that's just 5mm of your new 585 - 5mm in cockpit differential is acceptable) or as long as 475 (my guess was 473) or any where in between all with the same 90mm stem.

OPTION TWO: Order a QR PRsix size 50 with a 75mm stem and again you can cover a Pad Y rage of 580 to 675 and a Pad X range of 385 to 470 - and everything in between.

Now, I'd like to end with an apology. I'm bike fitter. I believe in bike fit. I educate fitters. Bike fitting results in more people on bikes. I've seen athletes come in to my studio with an FTP of 230 and leave with an FTP of 255 -just from a change of position. I've seen athletes come into fit studios so uncomfortable on their bike that they are ready to give up state secrets and leave joyful. I've seen athletes come into fit studios with horrible drag and leave slippery. Also, I led coaching education for USA Triathlon for a decade and I demanded that coaches got their athletes to get fit before buying a bike. You did just that, you did the right thing, but I'm 99% sure were mishandled by your fitter. I don't know what went on there, I don't why the Bermuda Triangle repositioned iteself over that fit studio - maybe it's a result of global climate change. I don't know why Rod Serling became a bike fitter and welcomed you into his Twilight Zone Fit & Coffee Salon. I just want to apologize that you had a less than perfect fit experience. There not all like that. Hang in there.

Ian

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Ian Murray
http://www.TriathlonTrainingSeries.com
I like the pursuit of mastery
Twitter - @TriCoachIan

Ian,

I went with a PRSix, size 50, 75mm stem. Hopefully I've escaped the Bermuda triangle now too 😂

Thanks for all of your help on this -- I'll just have to work on dialing in the fit myself over the course of training. Hopefully good to go come time for the Santa Cruz half-iron in September.

If anybody else is new to this thread and wondering if it's worth posting here to find out your proper fit, I can thoroughly endorse doing so. Ian goes way above and beyond.

Thanks,

Brett

Thanks Brett. When you get the bike if you want to set it up level on a trainer and submit a profile video we (the Slowtwitch Forum community) will share our thoughts on your position.

Ian

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Ian Murray
http://www.TriathlonTrainingSeries.com
I like the pursuit of mastery
Twitter - @TriCoachIan

Hi Ian -

Cross-posted from one of the other fit forums! Would love your opinion on the best size QR.


Cheers, Pat


Existing bike - Small Trek TTT (OG) with 165mm crank and the XXX cockpit with profile straight bars. My fitter is conservative on stack, but at 44, I'm ok with that right now. I'm 5'6 w/ 81cm inseam.


Top of saddle to center of pedal spindle = 89 cm


Nose of saddle to bar/stem intersection = 47 cm with ISM Breakway saddle
Top of saddle to top of bars = -100 mm
KOP = + 75 mm
Saddle tilt = - 3.5 degrees


STA = 80.5 degrees *
TT = 50 cm c to c LEVEL *
ST = 55 cm *
Stand Over = 80.5 cm MAXIMUM


Frame coordinates
Y = 55 cm +
X = 39.5 cm -


(*) off size cycle


Stem = 9 cm @ -17 degrees with 7.5 cm rise along the HT (off size cycle) w 42 cm BASE Bars


Approx X-Y for the aero pad:
Y= 66.5 cm
X = 48.5 cm

mrpeters,
I swear to you I've typed this answer on two previous occasions and it hasn't posted. I'm trying again...thx for your patience.

"fine, not comfortable, I can tolerate it" are all unacceptable references to the tri position. I want to urge you to get comfortable via bike fit.

482 sounds like a very good Pad X for you. The Pad Y of 724 however is a bit suspect. I'm thinking 650-660 makes more sense. Not sure how or why you're there - of even if you're there.

PRfive size 56 with a 90mm stem. Now, here's where it gets fun and funky! If you put that stem in the pointy-up direction at +17deg and you put a 10mm spacer under the stem and 10mm of pedestal under the aerobars you'll have 726 in Pad Y. AND... if you flip that same stem so that it's in a -17deg position and leave 10mm of spacer under the stem and slam the aerobars you'll have 661 in Pad Y. And, of course your Pad X of 480ish can be achevied with the same stem +17 or -17 - all based on where you bolt on the arm pads. Also, let's say we're both wrong and your Pad Y isn't 724 or 660 but somewhere in between this 54 with the 90mm stem can hit all points between with just a mix of spacers and pedestals.

Ian

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Ian Murray
http://www.TriathlonTrainingSeries.com
I like the pursuit of mastery
Twitter - @TriCoachIan

Pat,
As noted elsewhere previously... I'm going off the Pad Y and Pad X. I'm a wee bit suspicious and curious is Pad X is measured to center of pad. Let me know and I can tweak.

For the QR PRsix (or six2) it's a size 54 with the 110stem, mid clamp bar (the stem has a clam shell clamp for the base bar, put one half atop the base bar and the other half below) + 35mm of arm pad pedestal and you've got your 665. Put the arm rest bracket rearword and the armrest cup in the middle hole. This yields a Pad X of 485.

For the QR PRfive size 54 with 90mm stem in the -17 position with 30mm of spacer under the stem and 5mm pedestal. This gets you a Pad Y of 666 and then arm pads mounted one hold back from max forward and that gives you a Pad X of 486.

Ian

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Ian Murray
http://www.TriathlonTrainingSeries.com
I like the pursuit of mastery
Twitter - @TriCoachIan