I have completed 7 seasons of triathlon and my first 5 seasons I rode a road bike (Cannondale) that had 650cc wheels. I could never change a flat and my local LBS shop struggled with this as well, and both myself and my LBS mechanics broke tire levers trying to put tires on it. I finally found a tire that I could change on my 650cc’s but it was so soft that it took in everything on the road surface and I flatted constantly. I finally gave up and decided I’d find a bike that I could ride on 700cc wheels.
So, season 6 I purchased an XS Specialized Transition (tri bike) with 700cc wheels. As far as body position, I am very comfortable however I was surprised to find that I felt very unstable going down large/long hills. I had previously done IMLP twice on my bike with 650cc wheels and my maximum speed was 46-48 on the Keene descent and I was not scared. On my new bike with 700cc wheels I only hit 37mph on the same descend and was absolutely terrified. I am definitely scared on smaller hills around home but I use the Keene descent because it is so steep and I found myself breaking the whole way and hoping I didn’t flat from riding my brakes.
This feeling of instability affects me in any race that isn’t flat, and doesn’t make training fun at all. It is my least favorite part of triathlon to start with, and being fearful of falling off is a huge detractor. Season 7 I hardly rode my bike at all and it definietly showed in my bike splits.
I talked with the owner of my LBS shop, who was the one who both helped me select my tri bike and did my fitting, and he said something like “you should be able to ride 70mph on that bike down a hill.” So that was not helpful at all.
My theory is that my bike is all wheels and no frame, and that it is the equivalent of riding a circus bike. I am exaggerating of course, but that is what it feels like. In fact, my XS bike with 700cc wheels, the frame is so small I can barely squeeze in one tiny bike bottle in the cage below me. On my old bike with 650cc wheels I could fit TWO 24 oz Nalgene bike bottles in the cages below me. This makes me unhappy from an ease of carrying fluids standpoint, however I mention this because this shows how tiny my newer bike frame is.
Any thoughts on whether I am assuming correctly that the wheels are just too big for the frame, causing me to feel unstable? Any thoughts would be greatly appreciated!
Your description could be right on, hate to say it. There comes a point on small frames with 700c wheels were a lot of compromises need to be made designing the frame around the wheels. So it could be a factor of the frames geometry and weight distribution- where you a sitting on the frame.
Also, problems changing any tire depends on the rim type and tire, nothing to do with the size. Maybe you could go back to your Cannondale and get a rim/ wheelset that you can change tires on.
Thanks for your reply. I am hoping that it could be something else so that there is a bike out there with 700cc wheels that would work for me. But maybe not.
Most people with 650cc wheels find it much more difficult to get the tire on than 700cc wheels. I have tried two different 650cc wheels and probably tried every tire they make in that size! I can get my tires on my 700cc wheels with my bare hands.
my theory is that you are on a tri bike for the first time, and either not used to it or have a funky position on it that makes it unstable, or it is an ill fitting setup.
There are a number of things that could affect your stability, weight fore/aft. Having too much weight on the front wheel will tend to feel squirrly (this can be an issue with some TT positions), check the bike wheelbase, headtube angle. The more slack the head tube (lower number) the more stable usually, longer wheelbases feel more stable.
It can be difficult but you can in theory check weight fore/aft using a scale and a trainer. Set the bike up on the trainer, make sure the scale makes your bike level. Get on the trainer and into position. Check the number, now weight your whole body + equipment on the trainer. From these 2 you can figure out weight on the rear of the bike. My exerience is that you definately don’t want more weight on the front than the rear and even 50/50 can feel squirrly.
Thanks. I don’t totally follow how/what to check but I’ll have someone help me out with what you are saying I should check. But my question to you is, if I find that my weight is too much on the front wheel, are there ways to fix that or does it just mean I bought a bike that will always be unstable for me?
My previous bike that I felt totally comfortable and stable on, I am much more stretched out when I am in my aerobars so I tend to think that this could be a possibility as to what is causing me to feel unstable.
You don’t say what’s going on with the bike only that you feel unstable. What exactly is the problem. I’m with Jack on this; it’s likely that the problem is your new position. Try moving you seat back closer to your Cannondale position and adjust everything else accordingly. Possibly if you get closer to your old position and less out over the front wheel, you won’t feel unstable.
When I rode 650’s, I used Continental Grand Prix tires and I could get them on and off with just my hands.
Sorry to hear this. Nothing worse then riding a bike you’re not confident in / comfortable with.
On the road bike, did you have a TT bar setup, or road bars with clip-ons? When descending on the road bike, where were your hands? How about with the new tri bike?
Head angle 69.5 degrees
Fork offset 49 mm
Trail 75 mm
Comparing trail to other bikes, this one is pretty high.
Too much trail makes the bike “too” stable; it’s hard to get it to turn. Feels like it won’t turn enough, which can give the rider the feeling the bike is trying to straighten up and go off the road, towards the outside of the turn.
Search for Slowman’s articles on steering geometry and have a look at his recommendations for trail.
The solution is to reduce the trail to within a normal range, either by changing the fork to one with more offset (the 3T Funda fork is available in 53 mm of offset) or changing the frame to one with a steeper head tube angle. Unfortunately, that means a different bike.
The clue is your XS bike size. Very small frames with 700C wheels sometimes have to accept compromises in the steering geometry.
It’s hard to describe what exactly why I feel unstable. I just feel like I am about to go out of control and I’m not going to test whether or not I am correct or not.
What kind of wheels did you have when you rode 650’s? I am willing to try different wheel possibilities on my old bike, I just haven’t found many people that have had your experience of having an easy time getting tires on and off of 650’s. As I mentioned, the mechanics at my LBS who never used levers would be using multiple levers and breaking them on my 650’s. I have small friends who ride 650’s and have the same issue as well.
On my road bike, I had clip on aerobars. On my tri bike, I feel like my hands are in a similar position. But I have much more elbow bend on my tri bike because I’m not as stretched out.
Damon,
Thanks for the info. Does the trail have anything to do with going straight, but downhill and fast? Or do the stats you refer to only have to do with turning the bike? I am mainly referring to when I am going straight, but downhill and fast in particular.
Spinergy Rev-X. Now very obsolete. Have you tried Continental Grand Prix 23c tires?
What about your position on the new bike? My wife was a very good triathlete, going sub 5 hours for a half IM and qualifying and racing in Kona on a Cannondale road bike. When she got her Kestrel Talon, it came with a base bar and aerobars and she didn’t feel comfortable on it. The Talon is basically a road bike so I changed everything to match her Cannondale positon with drop bars and she was fine. She still has the old Cannondale though and loves to ride it.
Too much trail feels bad when cornering, yes, but even going “straight” we’re always turning slightly. Too much stability makes the bike less responsive to all steering inputs, even the desirable ones. But your comment makes me suspect there could also be a different explanation. Hopefully others will also chime in with other ideas.
In contrast to your 650C road bike, which probably has steeper head tube angle, less fork offset, less trail but certainly has less wheel rotational inertia (about the steering axis, not the hub axis) - your steering experience spans the spectrum. You have two bikes that handle about as different as anyone has ever ridden. Assuming basically normal production bikes.
If cornering isn’t the main critical moment for you, then my geometry explanation is looking weak. Could you maybe train your reflexes to better match the new bike’s handling? I’m assuming the bike is in basic, good mechanical condition e.g. no binding in the headset bearings or cables pulling asymmetrically on the steering, etc.
i don’t have any sage advice but found your post interesting. i have 650 wheels on my TT bike and 700’s on my road bike and have never noticed a difference in handling based on wheel size. that said, i just got a super light new to me race wheel for the front of my TT bike (instead of an older hed trispoke clincher) and that takes some getting used to.
i have also never had an issue getting tires on/off my 650 spoked wheels. i am having a harder time finding shops that stock 650 tubes and tires
Interesting, I had Spinergy 650’s as well, but I don’t think they were Rev-X. Since I stopped riding the Cannondale in 2011 I cannot recall all the tires I tried but I really left no stone unturned before finally deciding to go to a bike with 700cc wheels. I solved my tire changing problem but it never occurred to me that I would be unstable on a different bike. My Cannondale was my first bike I purchased and it was great.
From what you are saying about your wife’s bike fit, maybe I should take both bikes to my LBS and see what they can do to make my set up as close as possible to my Cannondale.
If that cannot be done and if I can figure out a wheel that I can get a tire on and off, I very possibly will go back to my old Cannondale.
I’m not sure what you mean by training my reflexes to better match my new bike handling. How would that be done? I did train for an Ironman on it, and raced IM on it as well. I would think that any training of my reflexes would naturally happen simply by spending time on my bike, which did not happen. And that was 2011; I rode it during 2012 as well and no improvement at all. If there is some specific way to train my reflexes other than spending time on the bike, I am interested to try it!
What kind of wheels? I am open to trying a different set of 650 wheels on my Cannondale. I am curious as to what 650’s you have?
I agree, it is hard to find 650 tubes/tires in stock at the local LBS. I always ordered mine and stocked up. Kind of a pain, but not as big of a deal as actually not being able to put them on!
I also rode my first tris on a road bike w/ clip-on bars (but 700c wheels).
When I first rode my tri bike (650c wheels), I thought it felt insanely unstable going down the steeps.
I raised my saddle and tilted it slightly back to make it level, and that eliminated the instability (feeling) for me.
Your source may be different, of course. Just sharing my experience in case it helps.
