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Tire experts...please weigh in.
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I have an upcoming 12 hour time trial. The race is on a fairly brutal course with over 10,000 feet of climbing in the first 110 miles. The roads are also pretty sketchy in places, lots rough chip seal pavement, cattle guards, expansion cracks, etc.

In the past, I have run zipp 404's with 23mm pro3race tires & latex tubes and I've taken a pretty good beating. I pre rode the course recently and there are couple sections where I was getting finger numbness just from road buzz. (and that was on my Cervelo RS, which is pretty plush)

I have the option of running zipp 101's or zipp 404s. I've never tried tires wider than 23's but I'm wondering if I should put a 25 on the back or even use two 25's.

What do you guys think the optimum combination of wheels & tires will be to put an emphasis on comfort but not sacrifice excessive speed?

FWIW - I'm about 170lbs and typically run about 115 for tire pressure on my p3race tires.
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Re: Tire experts...please weigh in. [BK] [ In reply to ]
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For starters, 115psi is probably too high. Are PR3's even rated to 115? The 23's might be, I guess. I think the 25's are only rated to 109psi. I think you should be down near 90psi in the front and 100psi in the rear. that might make a world of difference. Just my 2cents.
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Re: Tire experts...please weigh in. [tkeru408] [ In reply to ]
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Thanks for the feedback.

Yes, the 23's are definitely rated higher than the 25's. http://www.michelinbicycletire.com/...ent=airpressure.view
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Re: Tire experts...please weigh in. [BK] [ In reply to ]
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wow, what an incredible TT! - don't really consider myself and expert at this but i have done a few 56mile stand alone TT's and numerous 70.3's. i second "Tkeru" response to your excessive tire pressure. even at only 130lbs and riding tubulars, i never race at over 105psi - even for the rear. as for tire width, i'm curious of more opinions as you have a very serious course to contend with. good luck!
Last edited by: oc3ram: Sep 3, 10 10:10
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Re: Tire experts...please weigh in. [oc3ram] [ In reply to ]
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Are there disadvantages to riding PR3's at say 115 - 120 psi?
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Re: Tire experts...please weigh in. [gatormu] [ In reply to ]
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yes unless you're heavy. 1) rolling resistance penalty 2) you get the *$(# beaten out of you ala the OP.
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Re: Tire experts...please weigh in. [jpb] [ In reply to ]
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A rolling resistance penalty? Is that per USAT? What about tubulars...can they get a "rolling resistance penalty".

Sorry...I have never heard of a rolling resistance penalty...nor do I know how they would enforce that.
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Re: Tire experts...please weigh in. [gatormu] [ In reply to ]
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are you being deliberately dense? What I mean by rolling resistance penalty is that your rolling resistance is higher at 115-120 than it would be at 105 or so (for typical triathlete weights on a 23mm tire).
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Re: Tire experts...please weigh in. [jpb] [ In reply to ]
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Wasn't kidding. I always assumed the higher the psi (under 130) the better.
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Re: Tire experts...please weigh in. [gatormu] [ In reply to ]
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gotta consider rider weight, course surface, etc. OP said the roads are rough, cracks, chip seal etc. @ my weight i wouldn't ride any higher than around 100psi. not sure how much you weigh, but 115psi would be to much for most people. IMO
Last edited by: oc3ram: Sep 3, 10 10:17
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Re: Tire experts...please weigh in. [oc3ram] [ In reply to ]
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Weigh 150
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Re: Tire experts...please weigh in. [gatormu] [ In reply to ]
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maybe 105psi +/- on "that course" tops.
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Re: Tire experts...please weigh in. [gatormu] [ In reply to ]
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ah. Well then. The reason higher is not always better is because of surface roughness. You have to trade off between minimizing tire flex which absorbs energy, and minimizing "bounce" (turning your forward motion into upward motion when you hit small bumps in the road) which also costs energy.

On real roads that tends to occur much lower than 130 for the majority of people.
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Re: Tire experts...please weigh in. [gatormu] [ In reply to ]
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There is a chart on one of these threads that shows rolling resistance decreasing as PSI increases - but only to a certain point. At a certain PSI, all of a sudden rolling resistance increases greatly as the PSI increases (someone correct me if I am not remembering correctly). Seems counter intuitive, but that is what the chart says, so I go with about 105 for my P3s (weigh 155-160).
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Re: Tire experts...please weigh in. [The Guardian] [ In reply to ]
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If anyone has the chart I would really appreciate it. Good stuff all!
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Re: Tire experts...please weigh in. [oc3ram] [ In reply to ]
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In Reply To:
gotta consider rider weight, course surface, etc. OP said the roads are rough, cracks, chip seal etc. @ my weight i wouldn't ride any higher than around 100psi. not sure how much you weigh, but 115psi would be to much for most people. IMO

OP here. I don't disagree with you but according to the Michelin chart you only need to weigh about 175 to ride their 23mm tires at 116. Granted 175 is pretty heavy for most hardcore racing cyclists but not for the general population. Personally I'm 6'2" and weigh anywhere from 168-175 depending on the time of year and my discipline level.

I was speaking very generally in the original post when I said I typically run 115. True for the rear but I normally run my front about 5lbs less. Last weekend when I pre rode the race course I went a lower in pressures but the rear tire felt pretty mushy. Of course my mistake was probably that I didn't account for the 70oz camelback + 2 btls + food for the long unsupported training ride (as there is not a single store on the very rural loop).

I guess I should look at dropping a few psi. I also still think I may want to look at running a 25mm tire, at least in the rear.
Last edited by: BK: Sep 3, 10 10:39
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Re: Tire experts...please weigh in. [BK] [ In reply to ]
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For such a long race I would go with what ever you have been training with. Don't change wheels or tire pressue if you have not spent any time with them.
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Re: Tire experts...please weigh in. [BK] [ In reply to ]
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If you are using latex on a 12 hour race, wouldn't you finish with your tires about 5-10 psi below what you started with? That's what I usually lose overnight. So I wouldn't take too much out of them, maybe down to 110.
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Re: Tire experts...please weigh in. [sdmike] [ In reply to ]
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Fair comment but they are my wheels and I've ridden both sets quite a lot lately so I'm very comfortable in how they handle and all that.

My real intent in coming in this thread was to get a better handle on the differences I might see going from 23 to 25mm tires (of the same brand) and other minor changes I could make to increase comfort a bit.

I am curious for your logic though. I certainly wouldn't change my position or throw new handlebars into the mix at this point as that would be foolish but I don't see how dropping a few lbs of pressure or using a wider tire is going to dramatically throw me off and it could have the potential to help quite a bit.
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Re: Tire experts...please weigh in. [torrey] [ In reply to ]
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In Reply To:
If you are using latex on a 12 hour race, wouldn't you finish with your tires about 5-10 psi below what you started with? That's what I usually lose overnight. So I wouldn't take too much out of them, maybe down to 110.

Good point.
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Re: Tire experts...please weigh in. [BK] [ In reply to ]
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I recommend riding a road bike with clip on bars for the, (it sounds like rare), - flat, smooth, sections.

If there's a lot of descending, and cattle guards, and choppy roads, - it's better to ride a bike that you can handle. If you've got a lot of climbing and descending, - you're not going to be spending too much time in a TT position anyway.

I know that Zipps are great wheels, - but you may want to consider alloy. That being said, I rode most of the 508, - nasty roads, - on a pair of Carbon Reynolds Attacks with Continental GatorSkins, - those darn things were BULLETPROOF!!

I also am not a believer in dropping tire pressure, - it just slows you down and will cause you to flat. I believe that riding high pressures help to prevent flats. These tires and wheels and can stand bursts of objects in excess of 400PSI, - so you'd be talking about comfort that you want want from more flexible frame. I never ride below 125 PSI.

I say, Continental Gatorskins
Road Bike,
Selle Anatomica Saddle.
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Re: Tire experts...please weigh in. [BK] [ In reply to ]
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http://www.raceacrossoregon.com/roftt

miles of chipseal, awsome expansion cracks, endless climbs and screaming decents... I would recommend solid rubber tires :) see you next week.

Jay
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Re: Tire experts...please weigh in. [Toenail] [ In reply to ]
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Thanks Toenail, appreciate the input. I've done this event before and I do ride a road bike with shorty clip ons.. I have some Hed flip lites to which I've added ceegee pads and some cut down profile jammer extensions.

In the race, you first do the long 114 mile loop I described with 10K + climbing. You then move on to a shorter 26 mile loop which does have some climbing but "only" about 1400 feet total per lap. It's high desert and can be hot and windy. You keep going around the short loop until your 12 hours is up. There's a 24 hour race going at the same time so once you finish the 12hr, you collapse and watch the poor 24 hour suckers keep going by.

Some folks switch bikes throughout the event. Ride the mountainous section with a road bike and the more moderate part with a TT bike. Personally, I've been more in survival mode than race mode in the past and have stuck with my road bike.
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Re: Tire experts...please weigh in. [JBR] [ In reply to ]
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In Reply To:
http://www.raceacrossoregon.com/roftt

miles of chipseal, awsome expansion cracks, endless climbs and screaming decents... I would recommend solid rubber tires :) see you next week.

Thanks for that Jay. I'm definitely ready for a rematch after my implosion and early exit last year. Hopefully cooler this time around.
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Re: Tire experts...please weigh in. [BK] [ In reply to ]
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I'm rideing Michlin 23 Pro Threes on my Cervelo Dual. Have some "similar too" roads and will do a final shakedown on Sunday.

Jay
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