I'm running a Trek 2.3 (2010 model) and need to replace the damaged carbon fiber forks. The bike is size 56cm, has a 73.5 degree headtube, forks with 40mm rake (offset), 58mm trail and 983mm wheelbase (all data from the Trek catalogue). It's a stable and self-assured ride though perhaps it's a little too stable sometimes. I've seen a lovely pair of Ritchey forks but the the rake is 45mm. I appreciate how this will change the way the bike rides and feels via its impact on the trail (longer rake = shorter trail = livelier handling). My question is will the leap from 40mm rake to 45mm rake provide just a bit too much liveliness? Would I be better going for 43mm or maybe even sticking with safe 40mm?
All the dimensions of all the 56cm Trek bikes in the Madones, 2 series and 1 series (in the 2010 range), are the same (as mine, above). The dimensions change according to the size of the bike frame (for example, 54cm have 73 degree headtube, 45mm rake, 56mm trail and 981mm wheelbase). I guess there's a pretty good reason why they choose these configurations?
Doing a fork "upgrade" as you renew it is all well and good, but I'd check for the price of a Trek fork to replace your old one. It should have all the same geometry, it other words, no decisions or worries. If you liked the way the Trek handled, you'll still like this one.
Consider price in your comparison. I would not assume the Trek fork is not available and affordable.
Regarding tolerance, these are essentially factory made. Reasonable efforts are made to make them all the same. If a few mm tolerance is acceptable in fork blade length, we'd see front wheels routinely cocked in the bike.
But: I have a steel Trek road bike of the classic days that came with a 52 mm fork rake. It resulted in about 52 mm trail. I did not like the handling, too darty when climbing up slowly - kinda scary! I had the bike de-rakedto get a trail around 59 mm and it felt a lot more consistent when climbing. Not as good as my nice Italian Mondonico, but better. I've since had a high-rake (low-trail) fork made for the same bike, and now with about 35 mm trail I like it a lot. But that fork is a custom job.
Thanks for that. Good advice.
When I wrote about tolerance I was wondering if the 3mm difference between the Bontys and the Ritcheys would be enough to affect the bike's handling or if it wouldn't be an issue.