Stem Length

[2LeftCleats]

I'm generally satisfied with my riding position (Tarmac). The exception is on steep descents, reaching 35-40 mph, if there's any wind gust at all, I get tossed around pretty badly. Rim profile is 28 mm which probably contributes. Rather than buy low profile rims, would replacing the 100mm stem with 110mm would be an improvement? My thinking is that the longer stem requires more bar movement to turn a given no. of degrees, thus increasing stability. I doubt the slight loss of agility will be a concern. I also recognize this may require some compensatory seat repositioning.

Thanks.

[many_styles]

I mean it doesn’t hurt to try it. Find the same model stem but at 110.

But if you’re riding through some high winds it may or may not make a difference.

Had a 120mm stem and riding through 30-40 mph winds still sucked.


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[Peter P.]

No; replacing the stem will not solve your problem.

I had a similar problem. What I noticed was, a bike with a slacker head angle and higher trail figure (less fork rake) cured the problem.

I concluded this because another bike with different specs, on the same road under similar conditions did not have this problem.

So the next road bike I custom ordered had a slightly slacker head angle and higher trail figure, a paltry 2mm or so. It worked.

You could try a fork with less rake. That would be a cheap experiment if you bought a used fork on eBay. Then if it solved your problem, you could always buy a new fork for peace of mind.

Another check you could do is have the frame and fork alignment checked, even if it's carbon and not align-able.

[2LeftCleats]

Thanks. That makes sense.

[sheepdog84]

Maybe an apples to oranges comparison, but I've ran a 100mm stem on my Speedvagen - stock 58, and then swapped to a 110mm. The improvement in downhill, high speed stability was substantial.

It's also generally ill advised to change your fore/aft saddle position when swapping to a longer stem. Yes, you can get the same "reach" measurement for your fit, but it can also mess with your weight distribution over the bike. Maybe 10mm won't change a ton in your case? Just a thought. best of luck!

[benb]

Do you have your saddle position optimized?

If your weight is too far back it will exaggerate these effects in which case it may be OK to move the saddle especially if it turns out knees are way behind the pedal spindle. We can't make statements about "do this, don't do that" unless we know which pieces are already "correct".

If you are sure you have your setback right and you can't tolerate moving the saddle forward then you can't fix it with the saddle.

On the stem side if your stem is too short then lengthening it correctly would help, but if you can't handle stretching out more than that won't work.

Saddle too far back and stem too short can go together.. setup with the saddle to far back and you will want to shorten the stem.

[2LeftCleats]

Thanks again for the replies.

[track01]

Thanks from me too, good explanations.

[tv_vt]

I would certainly not worry about your rim height. 28mm is not catching a lot of crosswind. A longer stem and wider bars would make some improvement and is not too expensive to experiment with. Just start with longer stem. Are your bars on the very narrow side or more normal?

Agree that lengthening the trail would help too, without changing your riding position. If you have a basic swappable 1-1/8 fork like an Enve, Reynolds, Serotta, or whatever, going from a 43mm rake to 40mm would help, or 45 to 43mm. Less rake gives you higher trail, which slows the steering response a bit. (Edit- you say you're on a Tarmac, so swapping fork is probably not an option.)

There are other tricks/adjustments you can make, but they could affect riding position.

If your bike has a very high bottom bracket, that could also make it slightly less stable due to your higher center of gravity...

[TTrider]

I had similar issues for years and thought a slacker head tube angle, longer stem, wider bars, etc would fix it. These things did help but I found two root causes of this issue:

1. saddle too high
2. not enough weight on front wheel

Last one means either the front center on your current bike is too large or you're sitting very far back. Regardless moving forward to put more weight on the front will help, as well as lowering the saddle of course.

I went to a bike that had a steeper head angle, short stem (110mm coming from 140mm) and narrow bars. All of the things that would make the twitchiness worse I had - but the bike handled absolutely fine with proper saddle height (not too hight) and proper front-center (frame size/saddle setback.) I specifically remember a windy day when my friends were literally getting blown across the road and i was perfectly fine on my 60mm depth wheels because of my fit.

[rallizes]

Can we see a photo of the bike from the side?

[robt57]

Saddle setback, then stem length/bar reach together as one figure as needed.

Sounds like you are not in the middle of the bike's CG fore/aft window, rather at the edge or out of it.

[2LeftCleats]

I added 10 mm to stem length and that seemed to help a bit, but hard to be sure. What has made a bigger difference is deliberately shifting my weight forward on steep downhills.

Thanks again for the advice.