Custom build, funky handling?

[Lincoln]

Here's the background: A friend of mine has been getting more and more into riding the last few years. He has been riding a poor-fitting hand-me-down bike and has now gotten clearance from SWMBO to get a bike that fits. He went to Andy Pruitt (http://www.bch.org/sportsmedicine/bio-andy-pruitt.aspx) to get fit and was prescribed a very short top tube & fairly upright position (I think it was about a cm of drop--so not ridiculously upright) . He has some mobility issues in his hips and back and that is the main reason why the up and short position. Compounding this issue is that he has longer than average legs for his height and his femurs are especially long so once you accommodate that by adding extra set-back you end up with a very short TT.

We tried setting up a few of the off the shelf bikes that have a shorter & more upright geometry and we had to use such short & high stems that they rode (and looked) like doo-doo. Time to investigate custom. I think he is down to Serotta or a local custom builder. My concern is that the static position may meet the prescribed position but but what if it doesn't handle right (you know, it needs to plane ;) ).

Thoughts? Advice?

Thanks!

[goonster]

The approach seems very reasonable, but my advice would be to work with a builder who has experience building bikes like this.

Ask questions like, "here are my contact points, what adjustments to 'standard' geometry will you make to ensure the bike handles properly?"

The client needs get all his expectations straight in his head, and then communicate them clearly to the builder.

[acckids]

I have long legs and short torso and some low back restrictions(at the time) and I had a 63cm road bike built with a 56.5 top tube. Major issues with toe overlap. So much I sold it.

If I could do it over again, I would have requested something between the extremes. I would suggest he pick a builder he can speak to directly. A builder who brings up questions your friend might not even know(like toe clearance) to ask. At least a shop highly recommended by Serotta even if he has to drive 4hrs.

My custom build looked great on paper but the real world experience was different. I contribute it to me not knowing what to ask or request plus a bike shop who just plugged my measurements into a computer program.

I know go with 90mm stems and 40mm worth of spacers and have had great success.

[Smiley]

Any good builder will design around stuff like this, my only advice to make the bike handle well and reduce Toe Clip Overlap would be to look at a steel fork option with this builder. This is not as big a deal as you make it out to be. Done Short TT and Long ST bike designs forever but they all had longer trail numbers and tried to keep the stem no shorter than a 9 cm and used short reach set of bars.

[Peter P.]

You're assuming the Pruitt fit is GOSPEL. Well; I read his book and think his fit advice is excellent. BUT ALL THAT STUFF IN THE BOOK COULD BE WRONG!

Depending on how much faith you place in Dr. Pruitt's fit, he's anywhere from a guru to a nut case with regard to your friend's fit.

When things are that far from average setups, I recommend buying a cheap bike first, and experimenting with fit for a couple years, not trying to meet Andy Pruitt's numbers right off the bat but MAYBE getting reasonably close within the confines of a stock bike. You can even take into consideration the aesthetics as far as limiting how freaky you're willing to let the bike look while achieving Pruitt's fit numbers.

Another option is to take the Pruitt numbers to the local builder and say, "Hey; Pruitt says I should fit like THIS but I can't get a stock bike anywhere near this without the bike looking weird. Do these numbers make sense to you? Would you agree on the numbers or make changes?" Then take the local builder's information home and put it in your brain blender along with Andy Pruitt's information and see what makes sense to you and your friend.

I'm not a frame builder but in my opinion you CAN design a frame to FIT and design a bike's ride characteristics SEPARATELY. They will meet and the bike will ride fine.

[rpm]

Any good builder will design around stuff like this, my only advice to make the bike handle well and reduce Toe Clip Overlap would be to look at a steel fork option with this builder. This is not as big a deal as you make it out to be. Done Short TT and Long ST bike designs forever but they all had longer trail numbers and tried to keep the stem no shorter than a 9 cm and used short reach set of bars.

Avoiding toe clip overlap complicates things, especially if the rider has big feet. I have tall/short bikes from Strong and Serotta with "normal" 72-73 angles, trail, and wheelbases. They have tons of toe clip overlap, but that doesn't bother me. They look and handle just fine.

[Mike748]

I have a couple of custom 59ST/55-56TT bikes that handle great. Yeah they have toe overlap but its no big deal for me.

[AndrewS]

Toe clip overlap? Welcome to the world of everyone who rides the shorter half of the frame size range.

You friend probably does need a shortish top tube, and I've seen many, many of them made over the years. That is not an unusual situation.

If you have to go custom, don't dictate to a builder how to spec the geometry. Let the builder figure it out and do it their way. There is more than one "right" way to accommodate long femurs and short upper bodies. A good builder will come up with the best riding way to do it that works with his preferred handling principles. If the paper design is wildly different than the Pruit specs, THEN share them with the builder so some sense of the dichotomy can be made. Otherwise: Too many chefs spoil the soup.

I would be most tempted to use someone who is actually going to do the measuring and interview themselves (like Tom Kellogg), rather than working through the measurements of a third party, like a shop. I'm sure your regional availability and budget will dictate who you choose.

[pbjbike]

There are some great builders in the Boulder area: Mark Nobilette is one of the masters. Rich Gangl in Golden has a great rep, and Dean Bicycles in Gunbarrel if you want to go with Ti or carbon. It might be worth going to Vecchios in Boulder for a second opinion on the fitting. 72 degree head angle with 2+ inches of rake might be enough to avoid toe clip overlap.

[weisan]

Two words: Tom Kellogg.

[mtbmike]

I have the same build. Long femurs short torso. Forget square geometry (I.E. 58/58) typical with american bikes. I found some italian bikes have shorter T.T's (I.E. a 59 cm Colnago may have a 59 seat ube and 56.5 top tube) I think Basso had some dimensions like this with pretty tall head tubes as well.
There's aways Serotta.

[Smiley]

Avoiding toe clip overlap complicates things, especially if the rider has big feet. I have tall/short bikes from Strong and Serotta with "normal" 72-73 angles, trail, and wheelbases. They have tons of toe clip overlap, but that doesn't bother me. They look and handle just fine.

You never avoid it you minimize it. Keep the figure reasonable and your OK. I don't like a build to have more than 15 mm.

[I Want Sachs?]

9 Hours drive away from Boulder CO is Bozeman MT, where Kirk and Strong are. BTW. Any good National Park to visit on the way? Just kidding! :p (see closed thread)

[Ti Designs]

Two words: Tom Kellogg.


There's a case study here worth taking note of:

When Merlin started, they have the reputation of being the magic bike company. They sold entire size runs of frames that nobody had ever seen (my view of that time may be distorted, my shop sold three times as many Merlins as the second place dealer). What they couldn't afford was the reputation of making custom bikes that simply didn't work. Their solution was to make sell custom frames under the Spectrum name, which meant that the final say about geometry was up to Tom.

There's something to be learned there...

[chuckred]

and was prescribed a very short top tube & fairly upright position (I think it was about a cm of drop--so not ridiculously upright) .

I don't know if their system is in general "good" or "bad", but I also had a fit from one of his associates that ended up with a recommendation to have a shorter stem, more upright position. It caused more problems than it solved (although the seat height and fore-aft positioning seems fine). I ended up going back to my original position... I think good fitters fall into the trap of prescribing the same thing for everyone, and likely the great fitters prescribe different things for different people.

I've always heard that Pruitt is one of the "gurus", but that doesn't necessarily follow through to his staff...

I have a couple of friends who ride on Gangl's frames and both speak very highly of them.

[oldpotatoe]

Here's the background: A friend of mine has been getting more and more into riding the last few years. He has been riding a poor-fitting hand-me-down bike and has now gotten clearance from SWMBO to get a bike that fits. He went to Andy Pruitt (http://www.bch.org/sportsmedicine/bio-andy-pruitt.aspx) to get fit and was prescribed a very short top tube & fairly upright position (I think it was about a cm of drop--so not ridiculously upright) . He has some mobility issues in his hips and back and that is the main reason why the up and short position. Compounding this issue is that he has longer than average legs for his height and his femurs are especially long so once you accommodate that by adding extra set-back you end up with a very short TT.

We tried setting up a few of the off the shelf bikes that have a shorter & more upright geometry and we had to use such short & high stems that they rode (and looked) like doo-doo. Time to investigate custom. I think he is down to Serotta or a local custom builder. My concern is that the static position may meet the prescribed position but but what if it doesn't handle right (you know, it needs to plane ;) ).

Thoughts? Advice?

Thanks!

Waterford...custom.

http://www.waterfordbikes.com

They can be seen here

http://www.vecchios.com

[Dave]

There are some fitters who would pay no attention to femur length and set the rider's saddle position based on his weight balance over the saddle. That may or may not be as far back as suggested with the KOP method.

From my experience, even a short torsoed rider may require enough setback to place the knee 2cm behind the BB center. If the rider has long femurs that same setback might coincidentally be right on KOP.

It's hard to make an intelligent comment without the specific frame and rider dimensions.

If the frame's reach does not consider the use of a moderately short stem, maybe a 90-100mm and short reach bars (around 75mm), the suggested TT length may be shorter than necessary.

As far as handling is concerned, a more upright position reduces the weight on the front of the bike, but a shorter F-C increases it. More chainstay length will also put more weight on the front. I'd shoot for 45% on the front with rider in his most aggressive position - hands in the hooks and low torso angle.

The actual front/rear weight balance can be calculated fairly accurately, if you can get the rider sitting at about the same position on some other bike, with a known chainstay length and F-C.

[ergott]

Get a second opinion. Not because AP doesn't know what he is doing, but if the person in question doesn't fit the norm it's sound advise. Tom Kellog, Kirk, Hampsten and others are worth seeking out. Go with people that have great reputations for excellent handling bikes.

[nicrump]

im gonna go out on a very thin branch here and agree with eric. not that eric hangs out on thin branches, just that every time someone brings me a "fit" from the fitter mentioned in the OP, they seem to have these physical anomalies and require a TT shorter than my first home run experience with a chick.

the "fitter" may have the riders interest at heart but he doesn't understand performance bicycles and their associated geo's.

get limber, get fit and get a second opinion.