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Question on cornering characteristics(7 posts)

Question on cornering characteristicsMcAndrus
May 20, 2002 5:23 AM
I have a question for anyone who understands frames and forks well enough to give an opinion.

My main ride is a Giant CFR Team. You don't see many around so it might help if I explain that it most resembles a Look frame. In aggressive cornering and technical downhilling it has always felt a little sketchy, and I have to pay close attention. I wouldn't call it uncomfortable, I just have to watch my line closely.

A few months ago I cracked my old Bianchi Eros bottom bracket shell and sent it back to Bianchi for a warranty replacement. They replaced it with a Veloce frame. I had the LBS replace the Veloce's steel fork with a Kinesis carbon fork. The old Eros cornered pretty much the same as the Giant.

Yesterday I took the Veloce for it's inaugural ride. Just short of my house is the only fast corner on this ride, a downhill right turn that I usually take at 21 mph. On the Veloce I barely leaned into it and took the corner at 23. I could've gone much faster if I'd pushed it. It surprised me how I just kind of "thought" my way into the corner and the bike leaned over.

As far as my uneducated eye can tell, the geometries are similar, though there must be some difference. Before the Veloce's first ride, I made sure all the fit dimensions were the same - handlebar height, seat height, kop, etc.

Can anyone explain the factors that might account for the differences in cornering characteristics?
re: Question on cornering characteristicsgtx
May 20, 2002 8:41 AM
main factors are far as I'm concerned are head tube angle/fork rake and resulting trail, bb height, wheelbase and then your center of gravity on the bike and how it relates to all of the above. So in other words, lots of factors. For solid descending/cornering I like a fairly quick front end coupled with a slightly longer wheelbase and lower bb--alla Merckx.
I'll make some measurements tonightMcAndrus
May 20, 2002 9:02 AM
I'll check some other things when I get home tonight. I do know that the chainstays of the Bianchi are 1cm longer than those of the Giant. I can infer a longer wheelbase from this but I'll confirm that.

I'm also inferring from your comment that a slacker head tube angle may contribute to this. The dang Bianchi just carved its way through the corner, though, and I'd think a slacker headtube angle would make it less responsive instead of more.

For what it's worth, I've ridden a Trek 5500 and it handled very much like the Giant, which I guess would imply similar geometry, right?
Sometimes less responsive is better than moreRay Sachs
May 20, 2002 9:31 AM
Your ability to take the corner at a higher speed may be BECAUSE the bike is slightly less responsive, rather than in spite of it. Less responsive generally means more stable. More stable generally gives you more confidence to dive into a corner and keep it upright than quicker / more responsive. My personal opinion is that too many of the road bikes sold today are based on crit geometry that's just wrong for many of the recreational riders who are riding them. That quickness is good for moving around in a tight pack and maneuvering around really tight corners, but for your typical downhill corner or switchbacky descents, a bike with more stable handling is going to appeal to most recreational riders a lot more. I've ridden crit-quick frames and would almost always choose my more stable, but still plenty responsive sport-touring bike (unless I was racing in a crit, but I don't DO that).

-Ray
I'll make some measurements tonightgtx
May 20, 2002 12:06 PM
I'm not expert but you can't look at HTA alone--you have to factor the fork rake into the equation--you're looking for trail.

http://www.phred.org/~josh/bike/trail.html

My understanding is that bikes with low trail tend to be quicker handling at low speeds but firm up at higher speeds. But steering is just one factor--a bike that is too small for you can still seem twitchy even if it has very neutral steering as a result of a shorter than ideal wheelbase. And bikes will higher bbs just don't seem to corner as well. Again, that's my understanding.

http://www.rivendellbicycles.com/reader_articles/stiltstep.htm
And the results are:McAndrus
May 20, 2002 3:14 PM
The Giant has a one inch shorter wheelbase than the Bianchi and has .25 inch shorter chainstays. The bottom brackets are both 10.5 inches from the ground. I couldn't find my protractor and compass so I didn't try the rake and trail. Thanks guys. This stuff should be obvious to a geezer like me but hey, I can always learn more.

Oh, and sorry to do the measurements in English. It's been a long day and I'm too lazy to do the conversions.

Thanks again.
re: Question on cornering characteristicsSnowBlind
May 21, 2002 7:28 AM
Interesting, my old bike was a Veloce, and I had the experence of poor cornering compared to my current frame, an custom steel.

The funny thing is the Inglis is shorter than the Veloce, and handles much better. Exactly the opposite of what you found. There is one funky little hairpin turn that used to be sketchy on the Veloce at 18 mph, but I can take it at 25 and still pedaling on the Inglis. The bottom bracket hight is the same on both bikes.

I, personally, attribute this to the better fore/aft balance I have on the Inglis vs. the Veloce. This was one of the major things the builder tried to fix with the custom frame. Other local decents I have done on both bikes, the Inglis tracks better and feels stuck to the road compared to the Veloce. He made the seat tube a little slacker than the Veloce, and the top tube is dropped like your CFR (I think the CFR is dropped?). Countersteering is a scream on the Inglis, feels so natural.

Based on the "thought" comment, I wonder if you have had the same experence with better balence. The Inglis will "get" you if you disrespect it and try to man-handle it around a deep curve. Better to let the bike find the line, and just go with it. Took a while to break that habit.