Small wheel handling question: easier to wash out at high speeds?
 

So I got my bike friday rebuilt to be more in line with how I ride- 451 wheels with 1.125 primo comets, drop bars, etc.

Riding home last night, coming down a wet constant radius circular bike bridge (like a freeway off ramp), my front end washed out and I went down pretty hard, face first. Ouch. Nothing permanent- teeth are fine, bike isn't even scratched.

I've got a couple theories as to why I wiped out, thought I'd see if the esteemed forumites here could tell me if I'm right.

1: front tire was grossly under inflated. I saw it was low, thought about pumping it up, didn't. My guess here is that small wheels are a lot more sensative to low pressure than big ones.

2: Don't know the bike well enough to be riding it as hard as I was. I was pushing a bike I was very unfamiliar with, with very unique handling characteristics, a lot harder than I should have, especially given the conditions (hard rain just an hour before, roads very wet).

3: Just plain took the corner too fast. With the weird gearing you get with small wheels, I was pushing a 42/11 through the corner. On a traditional road bike, I might have slowed it down a bit. Plus, no speedometer on the Friday, so no idea how fast I was going. Figure between 17 and 20 mph when I went down.

4: all of the above.

If anyone has any thoughts about this, I'd love to hear it, even if they are "you're an idiot." Are there special concerns with smaller wheels- is there less traction in the wet or is this just a simple case of washout due to under inflation?

Obviously, my concern is that I'd not like to repeat this. Figure next time I'm not going to get so lucky.

Probably the under inflated front tire was the biggest factor. I don't think the tire size is a significant factor. Hasn't been with my 28mm 406 tires on my Pocket Expedition. I've taken corners with aggressive group rides with no issues. But I've slid the front tire with an underinflated front tire on 700c wheels as a result of a puncture. Wasn't completely flat, just low. Scary how little traction there is with a tire designed for high pressure when it is going flat.

Glad you weren't seriously hurt.

I'm doing the same thing as you with a new Bike Friday (having one built for the way I ride, not the crashing part hopefully). My fixed gear Pocket Rocket arrives on Friday. I'll use it for commuting & fast group rides.

Alex Wetmore once wrote that he didn't like the handling of Primo Comets in wet pavement. The context of the statement was that they had this reputation; but I never heard of that reputation from anyone other than him.

I think it is because your tires were under inflated. Wider tires, all things equal, will have better cornering traction. I don't think that the small wheels have much of an effect.

Hey, I'm sorry to hear about your accident. I'm glad to hear that you, primarily, and your bike, secondarily, were not hurt. That must have been scary!

I would just recommend as an overall note of caution to think twice about riding aggressively in what sounds like a risky setting: narrow, twisting ramp, wet road conditions, darkness (if it was after sunfall). When I think back on my bike accidents over the last few years, one was due to riding over an unseen embankment (it was after dark, and I didn't know the path), another from taking a downhill turn too fast, a third due to riding over a slick, mossy wooden bridge (it had been raining a lot that season), a fourth when I got hooked by a car (across an MUP, no less). Thankfully none of them permamently damaged me or my bike, and only one required an emergency room visit. But it's made me a lot more cautious riding in situations that strike me intuitively as a little scary--for example, if I can't see the path in front of me (because it's dark and unlit) or a hill seems dangerous to attempt, I'll go very slowly or dismount.

An under inflated tire will usually slow you down, but I don't see how it would be more likely to wash out unless you rolled the whole tire off the rim by cornering crazy hard. It's common to drop tire pressure to increase traction as you get a bigger contact patch. As the other folks have said I don't think your crash was a related to wheel size so much as factors #3 & #4 from your list above and maybe #1.

Keep in mind that even on a perfectly inflated tire it only takes a small patch of grease/oil or slippery metal for your front wheel to wash out in a turn.

BTW - I'm glad you and your Friday are okay...:thumb:

one thing I notice, on smaller wheeled bikes, the weight distribution, front to back, is not the same as a full sized bike.

This is actually the opposite- It's a path I ride almost every day- familiarity breeds overconfidence... whoops.

I'm guessing on the washout from having washed out under-inflated MTB tires in the past. On an MTB, you're often trying to balance the lowest pressure possible for best traction with bottoming/washing out... I looked at the tire again once I got off the bridge and I could see the tire rippling/deforming under my weight at a stop sign, so I added some air- it was really underinflated.

But I'm definitely willing to look at other possibilities.

Thanks all for the good wishes! I especially appreciate the feedback- I do not want to be scared of this bike.

This is kinda going to suck for the weekend- My wife and I are having our first overnight away from our daughter and we had planned for a nice spa getaway. As scraped up as I am right now I cannot imagine getting a massage or even getting into a hot tub. ugh.

As long as you're okay, that's the most important thing.

Actually this is not a fair statement, some manufacturers spend years getting their bikes evenly distributed and with the right geometry, the Reach by Pacific is a good example of this, they have spent years perfecting this, but unfortunately for them very few people think of ride quality when buying/recommending a folding bike.


Its a pity, since we spend more time seating in the bike than folding it.

I will say that even with the much skinnier tires, the Friday rode like an absolute dream- I was expecting the skinny tires to give it a much harsher ride, but it was smooth as silk.

I kinda feel like an early NASA spokesman- "Had it not been for the catastrophic failure 7 minutes into the test flight, it would have been perfect..."

"My own experience has gone no further than to 50 centimetre wheels furnished with 50 millimetre tyres, but I can guarantee that in an experiment extending as far as 15,000 kilometres covered, they will not have the smallest disadvantage from the point of view of their running. It simply seems to me they are more prone to skidding, but this is perhaps due to the fact that their tyres have no tread and that the bicycle is very short." - Velocio (the father of cyclotouring) 1911

http://www.users.globalnet.co.uk/%7E...e,%20small.jpg

That is why, five folding bikes later, I ride a Swift!

Going too fast for the prevailing conditions? Wheel size has nothing to do with it neither does tire width in my opinion. Could have just been a bad patch on the road.

I'd go with the underinflation as the primary problem. I certainly notice the effects of underinflation much quicker on my Bike Friday than on my 700c bikes. Mainly due to increased rolling resistance, but also unpredictable handling. The underinflated tire can have the sidewall roll under on turns which may have contributed to the crash.

I don't think you can blame it on wheel diameter.

While I mostly ride small wheeled bikes, the only time I've had washouts were on skinny tired big wheeled road bikes.

I've noticed that the "side motion" on my Brompton increases as I go faster and that if I hit a bump, I will swerve slightly. I thought it was the tires, but it was actually the little rubber suspension giving out.

Glad you're O.K. and you didn't damage the new BF. I'll keep your experiance in mind when My new Bike Friday come's in next week. Just bought one today and I can't wait to get her on the road/trail.

Chucky, you need to tilt your seat back a bit. :innocent:


OP :
Under-inflated tyre + wet road + bend in wet road + too much :speedy: = :bike2::crash:

The only time small wheeled bikes are more dangerous is if you are up against a mad Australian racing you on his modified R20 :D

Learning what is the right line and speed to take into that line when cornering and remaining calm and committed to that line will avoid most crashes

I've seen many people panic and brake unnecessarily when cornering, they're the one's that usually crash or cause crashes.

I was pleasantly surprised at how well my MODIFIED R20 cornered at a high speed downhill right hand turn, (remember that in Oz we ride on the left), I thought I was a goner, but the narrow 406 HP Contis stuck like glue.

Also learning that it might not be the same speed and line you took with a different bike seems important.

Like I said, this is a path I ride almost every day, and the bridge itself is brand new- no oil, just pure white concrete elevated about 20-30 feet over the road...

No panic braking- no time. Just "oh crap the front tire is washing out is it gonna catch nope going down please don't break my teeth please don't WHAM ouch no teeth broken"

Thanks! sorry I couldn't reply to your PM- apparently I have to have 50 posts before I can send PMs. Yer gonna love yer friday- it really does ride like a full sized bike. Just make sure the tires are properly inflated...

yes from experience, try for yourself, this will be probably the best way of answering the question for yourself.

an opinion is work about .01% of an experience.

I've got my own experience on the subject, and the road rash that comes with it. Now I need to find out if my experience was an aberration or the norm.