looking for advice regarding unstable sprints (fork issue?)

[jasonification]

Hello all! I'm looking for some advice.
- When sprinting with my steel Serotta, I've noticed that as I get up to speed, the bike becomes increasingly less stable, usually to the point where I would have to get back into the saddle to stabilize.
- I've noticed that I tend to be able to pull the handlebars to the right easier than the left.
- I had always thought it was my riding style until recently when I rode my brother's Cannondale SuperSix, and noticed I could get up to speed pretty quickly without feeling unstable
- I recall looking at the fork of my Serotta and noticing a slight asymmetry (might just be paranoia). Am wondering if this could be the issue, or if there might be other things that i should keep in mind?

[ultraman6970]

Just to start... post a picture of your bike. Hard to give you a reason w/o looking at the bike and your set up of it, but probably you have to lower the stem more.

[Lewis Moon]

A buggered fork will play havoc with your sprint. That said, one of the things I really hated about some bikes was the short top tube (front center, really). If you get too much weight out over the front wheel, things can go pear shaped pretty quickly.

[Dead Man]

I had a bike that was super squirrelly.. sprints, climbing out of the saddle, even just taking my hands off the bars, it wanted to flop around all over. I don't remember the progression of diagnostics, but the solution was a fork with more rake. Fixed it

[LegendRider]

A buggered fork will play havoc with your sprint. That said, one of the things I really hated about some bikes was the short top tube (front center, really). If you get too much weight out over the front wheel, things can go pear shaped pretty quickly.

Weight distribution is the first thing that I thought of too. Try sprinting with your butt further back and see what happens.

[JLP]

Sounds like you need to rule out a few things. I'd do the following:

Assuming nothing odd about weight distribution, then move on to the bike...

Make sure all the bearings are good. Hubs and headset. Does it do this with different sets of wheels? Is there any pitting at all in the headset? Check this with everything off the fork.

Is the rear wheel dished correctly?

Then move to frame. At the very least have someone use a frame alignment gage to ensure the bike is aligned. If that doesn't get you there, then on to alignment table.

Have a builder check the fork. If you have any suspicion at all about a fork issue, don't hesitate to have that checked out.

[jasonification]

Just to start... post a picture of your bike. Hard to give you a reason w/o looking at the bike and your set up of it, but probably you have to lower the stem more.

Photo attached! Am out of town so I don't have photos specific to the fork, but I did a short photoshoot a few months back of my bike..perhaps I need a longer rake?

[JLP]

No, you don't need to change the geometry. You need to make sure everything is working and straight.

[FlashUNC]

Photo attached! Am out of town so I don't have photos specific to the fork, but I did a short photoshoot a few months back of my bike..perhaps I need a longer rake?

Are you all torso and arms?

That frame looks too big for you, but tough to tell without seeing you on it.

[Ken Robb]

The stem looks rather long for that size bike so the bars look to be pretty far forward which would put a lot of weight on the front wheel. Then when you stand and lean forward there is even more weight out front. The non-set-back post also puts your weight toward the front so I think that could be your problem.

[Skenry]

So its less stable now than it used to be?
Or less stable than another one of your newer bikes?

I'm going to guess you have another bike at home and that its probably newer too. Looking at the Serotta, it looks to big, and I'm a fistfull of seatpost type of guy. It also looks like a 1" threaded stem with maybe a 130mm extension. You will flex the hell out of that, it was great, even top of he line back in the day, but nothing compared to a modern setup.

Provided everything is straight and true, compare it to the other bikes in your stable.
Scott

[jasonification]

The stem looks rather long for that size bike so the bars look to be pretty far forward which would put a lot of weight on the front wheel. Then when you stand and lean forward there is even more weight out front. The non-set-back post also puts your weight toward the front so I think that could be your problem.

Hi all,

Thanks for the great feedback and opinions so far. Looking back on the photo, it definitely does look like I put the seat far too low! I think it was right after a good and thorough scrub, but I assure you all that the seat has subsequently been raised to an appropriate height.

@Ken: the issue regarding weight distribution out of the saddle makes sense! Will try to see if I can address that...Thanks!

@Skenry: I can't say for sure right now (currently out of town), but you are probably right that the stem is a 130mm. but what you say about flex makes sense!

I've checked the hubs and everything is peachy keen on that end.

For now, it looks like the things to look out for/try are:
- change out the stem to something shorter
- check headset
- send fork to a frame builder if problem persists.

haven't had/ridden another bike until recently (this has been my first and only road bike! that situation may change soon though..:D).

Many thanks to all! Please keep opinions flooding in if there are a few more things to check. Otherwise, I will keep everyone posted once I get the chance!

Also, if getting a shorter stem should I consider a 110mm or a 120mm (assuming that the current stem is 130mm)?

[Dead Man]

I see the problem - you didn't time your tire label to the valve stem on the rear.

[jasonification]

I see the problem - you didn't time your tire label to the valve stem on the rear.

That problem has been remedied since that debacle ;)

[ultraman6970]

That is the reason why I asked for a picture...

Dont take me wrong ok, just trying to help you ok?

Frame is at least 3 cm too big. If thats a 56 center to top you have to fit at like a 54 ish. Never, but NEVER EVER (advice for anybody reading) get a bike because you like it, even if doesnt fit +-1 cm, anything more than that wont fit even if you can make it work. Then you end up with this fellow problems.

Jason, you have to find the right frame 1st, you can't make that one work my friend, even if you think you can, I do get that some guys have long arms and short legs like an orangutan but that doesnt mean you have to go off the logical frame sizing ranges just to fit your long torso, because the bike will get the center of mass in the wrong place and the frame starts acting up like yours do.

You need to start by finding the right frame my friend.

Maybe somebody has something to trade????

ps: is my personal opinion ok? take it with some salt and vinegar :D

[David Kirk]

Replace the fork to make it threadless and get rid of the super flexi quill stem and $100 says you will love it. Those stems are like diving boards without the fun part of getting wet.

dave

[jasonification]

Thanks for your input ultraman! No offense taken :D In fact, your opinions are much appreciated! For the most part (90% of the time), the bicycle handles very well. Perhaps because I haven't had much experience with other bike (this has been my first and only), I don't know what a "perfect fit" feels like, but I have thoroughly enjoyed putting miles on this steel specimen. I'm going to try to see if I can make this work! But your thoughts will be in the back of my mind if I can't remedy the situation..

That is the reason why I asked for a picture...

Dont take me wrong ok, just trying to help you ok?

Frame is at least 3 cm too big. If thats a 56 center to top you have to fit at like a 54 ish. Never, but NEVER EVER (advice for anybody reading) get a bike because you like it, even if doesnt fit +-1 cm, anything more than that wont fit even if you can make it work. Then you end up with this fellow problems.

Jason, you have to find the right frame 1st, you can't make that one work my friend, even if you think you can, I do get that some guys have long arms and short legs like an orangutan but that doesnt mean you have to go off the logical frame sizing ranges just to fit your long torso, because the bike will get the center of mass in the wrong place and the frame starts acting up like yours do.

You need to start by finding the right frame my friend.

Maybe somebody has something to trade????

ps: is my personal opinion ok? take it with some salt and vinegar :D

[jasonification]

Replace the fork to make it threadless and get rid of the super flexi quill stem and $100 says you will love it. Those stems are like diving boards without the fun part of getting wet.

dave

looks like I need to start looking out for a new fork!

[David Tollefson]

How worn is the tire? If the tread wear is uneven from the road crown, it could have an uneven effect left vs. right (as you described).

[djg21]

The stem looks rather long for that size bike so the bars look to be pretty far forward which would put a lot of weight on the front wheel. Then when you stand and lean forward there is even more weight out front. The non-set-back post also puts your weight toward the front so I think that could be your problem.

This was my sense too. The frame also looks like it is too tall for you if your seat-height is set properly. And if you need that much stem with deep drop bars to get the proper reach, even on a bike that is that tall, something is wrong with your fit. Those old quill stems also would flex a significant amount, especially if overly long. I remember the huge difference I experienced swapping a cinelli quill stem for a Salsa Chro-mo quill stem.

[LegendRider]

Replace the fork to make it threadless and get rid of the super flexi quill stem and $100 says you will love it. Those stems are like diving boards without the fun part of getting wet.

dave

Dave,

I remember Davis Phinney talking about moving from a Cinelli XA stem to a Synchros and noticing a huge difference. If I recall correctly he said the the XA flexed with a rhythm while he sprinted, but the Synchros was so stiff he'd practically pull the front wheel off the ground. Does that sound familiar?

[David Kirk]

looks like I need to start looking out for a new fork!

Even going to a tubular style quill stem will be much better - I'll bet they can be found on the cheap and would be worth trying.

The real issue is twofold - first the interface between the stem and fork is inherently flexible and there is nothing to be done about that. Secondly the cross section of the forged alloy stem is very small and will be very soft in torsion. That long elegant stem strut will move all over the place. Just trying sitting on the bike and then grab the bars in the drops and push one side down while pulling the opposite side up and watch it twist.

By swapping out the forged solid stem with a tubular stem you will dramatically reduce the twist in the stem itself. If you want to take it to the next level have a threadless fork built for it and take out the movement in the interface and it will feel rock solid.

I hope that helps -

dave

[David Kirk]

Dave,

I remember Davis Phinney talking about moving from a Cinelli XA stem to a Synchros and noticing a huge difference. If I recall correctly he said the the XA flexed with a rhythm while he sprinted, but the Synchros was so stiff he'd practically pull the front wheel off the ground. Does that sound familiar?

Yeah - very familiar. Those forged aluminum stems are like wet rags - not good. I know folks like the way they look and some think that there's no difference between a solid forged stem and a tubular stem but that just isn't the case.

dave

[ultraman6970]

Thanks you take it nicely, many times there;s no other way to say it, thats the main reason I cant work in a LBS :D

Hope you can fix it :) shorter stem will help for sure.



Thanks for your input ultraman! No offense taken :D In fact, your opinions are much appreciated! For the most part (90% of the time), the bicycle handles very well. Perhaps because I haven't had much experience with other bike (this has been my first and only), I don't know what a "perfect fit" feels like, but I have thoroughly enjoyed putting miles on this steel specimen. I'm going to try to see if I can make this work! But your thoughts will be in the back of my mind if I can't remedy the situation..

[carpediemracing]

http://forums.thepaceline.net/attachment.php?attachmentid=1697910787&stc=1&d=1448384508

When sprinting out of the saddle one relationship you have to make sure stays about the same is the BB->drops relationship. Since you're not sitting you don't need to worry about the saddle position in this situation.

Measure BB height from the ground, drops height from the ground, and compare the two bikes. I'm curious what you find.

Also, the SuperSix has a tapered fork and an ultra rigid front end (laterally). My SystemSix, which is similar (stiffer?) was absolutely incredible when out of the saddle or when cornering, it was by far the best handling front end I've ever ridden. I could go into one of my "test corners" a solid 4-5 mph faster without feeling like I had to back off. It's a downhill turn, approach speed about 45 mph, and on the 5 bikes I've ridden in that corner my speeds were typically in the 35-38 mph range, on the SystemSix I hit it almost flat out at about 42 mph.

An n=1 study, on my own (post-SystemSix) custom geometry non-tapered-fork aluminum frame bike. I put a TON of weight on the front of my bike, enough so that on a 40.5 cm chainstay I'd regularly skate the rear wheel sideways while coasting in turns. This prompted me to get a 39 cm stay, fixing the problem, or, for the critics, eliminating the symptom.

A couple years ago I decided it'd be best to replace my 25 year old bars (crit bend Mavics/3ttt). I really liked the feel of the FSA Wing Compact bars. Problem was that it had 3 cm less reach and 3 cm less drop than my crit bend bars. I got a 2.5 cm longer stem, so I gained back most of the length.

However the bars were 3 cm higher than what I was used to.

I started having massive problems sprinting (out of saddle, on drops). I've been fine sprinting for decades (and for years on the custom geometry) and suddenly, with the FSA bars, I wasn't really in control of the bike. Front end felt like I was on a 36" tall wheel. I couldn't keep the front end planted, even with my extreme forward position. I felt really uncomfortable really uncorking a sprint because I felt out of control. I had a bunch of "failures" (unclipped a bunch of times, dropped chains, etc) so I chased seemingly imaginary mechanicals for a while.

Then, for whatever reason, I got on my other bike, with the crit bend bars and the normal stem (and therefore I'd gain back my lost 3 cm drop). I felt 1000% stable again.

I decided to order a stem to place the drops of my FSA Compact bars exactly where the crit bend bar drops sat. I had to find 3 cm reach, 3 cm drop, and ended up with a nutty stem (-32, 145mm). I settled for 2.5 cm more reach, vs 3 cm. Ordered it custom.

First time after installing said stem on the bike and it felt 1000%. No mysterious mechanicals, no weirdness in the sprints. 100%. Drops were back where they were "supposed to be" and the bike felt normal again.

Same frame, fork, wheels, even tires (I've used the same two pairs of tires for 4 or 5 years). Over the couple years I dealt with the sprint issues I went through a couple chains and 1 set of cassettes, but the bike was the same otherwise.

[tv_vt]

You have checked to be sure the fork isn't cracked? Everything is bolted down tight?

Otherwise, it seems like Dave Kirk has pointed you in the right direction.

[bicycletricycle]

I don't think you can say a bike is the wrong size until you see the person riding it.

Like many people have said, the older smaller diameter steerer tubes and quill stems will be much flexier than the huge diameter stuff found on most bikes today.

That being said, some people were able to rip some pretty fast sprints on "outdated" flexy equipment like that.

Stiffer and more stable for the sprints will most likely yield a less comfortable bike for the rest of your ride.