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tatfiend 05-19-09 03:53 PM

Front End Geometry Question
 
What is the effect of reduced trail on bike handling? I note that photos of many older bikes, including French Randonneuring bikes and Raleigh roadsters, show large amounts of fork forward curvature compared to current designs. This appears like it would reduce trail on the bikes compared to most current designs.

Does this aid handling with a front load on the bike? What are the advantages and disadvantages of such geometry and why is it no longer common?

Scooper 05-19-09 04:19 PM

Dave Moulton's blog: Trail, fork rake, and a little bit of history.

DannoXYZ 05-20-09 02:15 AM

Quote:

Originally Posted by tatfiend (Post 8947804)
What is the effect of reduced trail on bike handling? I note that photos of many older bikes, including French Randonneuring bikes and Raleigh roadsters, show large amounts of fork forward curvature compared to current designs. This appears like it would reduce trail on the bikes compared to most current designs.

Does this aid handling with a front load on the bike? What are the advantages and disadvantages of such geometry and why is it no longer common?

The headtube angle is probably not as steep as today's bikes. This effectively gives the larger rake more trail.

unterhausen 05-20-09 07:41 AM

many of these bikes do have less trail, which is said to improve handling with weight over the front wheel

Road Fan 05-26-09 07:51 AM

Jan Heine (wrote the picture book on randonneuses) has written in the Bob list, that the head angles of French randonneues are usually in the 73 or 74 degree range, so pretty steep actually. They use a big rake or offset to reduce the trail and facilitate fork springiness, and presumably long top tubes to reduce toe overlap.

tuz 05-26-09 09:14 AM

I thought it was the opposite: slacker 72 degrees head angle (high trail) with long rake to reduce the trail and toe-overlap.

Longfemur 05-26-09 10:25 AM

They have to use longer top tubes on those bikes not as the preferred method of avoiding toe clip overlap, but as a result of other front end geometry choices they have made. It was necessary in order to push the front wheel and fender far enough from the pedals. This is one reason for the old "French fit" idea... the bikes were so long that most people did end up having to have the bars as high as the saddle in order to ride them. It was also one of the factors for use of 650B wheels. Of course, that's generalizing. Not all bikes intended for randonneurs were exactly the same.

Road Fan 05-27-09 08:20 PM

Yes, a better way for me to have said it is that toe overlap was avoided and balance was set by locating the entire head tube and fork subassembly out far away from the seat lug.


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