Please school me on forks

[velomateo]

I recently had the good fortune to score a National Team GT. The bike is in excellent condition, I don't believe it has ever been raced and barely ridden. This bike is one of the Reynolds frames, not the earlier True Temper model, and came with an aluminum fork. I'm not a fan of aluminum forks, and would like to replace the fork with either a steel or carbon model.
There's a thread across the hall about these frames, that includes an email from Koichi Yamaguchi - he was involved in the design of these bikes. Koichi states that the fork offset for these bikes was 45mm. Assuming that dimension is correct for my bike, would installing a fork with an offset of 40mm or 43mm adversely effect the bike's stance or handling?
There's a Waterford fork available locally, made with Henry James drops and crown, at a very good price. From the Waterford website, this fork should have a 40mm offset. Also, there are some Ritchey Carbon forks, on eBay, that have a 43mm offset.
Any info or experience you could pass along is appreciated.

http://i238.photobucket.com/albums/ff297/velomateo/Saturn%20GT%20team%20bike/3C569B32-E92B-4899-A2A4-BE1934314419_zpsef0o8scu.jpg (http://s238.photobucket.com/user/velomateo/media/Saturn%20GT%20team%20bike/3C569B32-E92B-4899-A2A4-BE1934314419_zpsef0o8scu.jpg.html)

[unterhausen]

changing axle to crown makes much more difference than a few mm of rake. Be careful if you propose to do both. There are lots of 45mm rake forks out there

[FlashUNC]

Why not go whole hog and see if Yamaguchi would make a matching fork for the frame?

Then you side step the geo question entirely.

[sandyrs]

45 to 43 will almost certainly have no discernible effect. 45 to 40 might be slightly noticeable but there is no guarantee it will be adverse, might just behave ever so slightly differently in corners.

[velomateo]

changing axle to crown makes much more difference than a few mm of rake. Be careful if you propose to do both. There are lots of 45mm rake forks out there

Yeah, I don't want to go longer/shorter.

[velomateo]

Why not go whole hog and see if Yamaguchi would make a matching fork for the frame?

Then you side step the geo question entirely.

That would be cool, but I'm certain that would blow a large amount of my budget. Yamaguchi didn't actually build the road frames, he was involved in design, but I believe he did build the track bikes. Dave Tiemeyer did the road frames - and he's since retired.

[velomateo]

45 to 43 will almost certainly have no discernible effect. 45 to 40 might be slightly noticeable but there is no guarantee it will be adverse, might just behave ever so slightly differently in corners.

Thanks. That's kind and of what I was thinking. I don't want to cause the frame to sit nose high/low either.

[berserk87]

Sorry to derail the thread, but I remember those GT national team bikes when they were new. I think that they are made of Reynolds 853 steel.

Having owned a GT, I can say that I was not a huge fan of the triple triangle design, but I loved the paint scheme. Nice score on this road rig, by the way.

[Peter P.]

45 to 43 will almost certainly have no discernible effect. 45 to 40 might be slightly noticeable but there is no guarantee it will be adverse, might just behave ever so slightly differently in corners.

I agree with sandyrs. My experience has been that 5mm will be noticeable but whether you like it or not is subjective. Dave Moulton's Fuso frames had less rake than 40mm with a 73 degree head angle and yet his frames were very popular.

The difference between 45 and 43 will likely not be noticeable. I'd be more concerned with a change in axle to crown length. Here again, my experience has been a 5mm difference in fork length will definitely change the way a bike handles.

[Fivethumbs]

I noticed a difference in handling from the reduced trail when I went from a 42mm offset to 45mm.

[Heisenberg]

Rake extrapolates.

2mm is relatively minor. 5mm is fairly big. The longer rake fork you install, you will increase steering speed (decrease trail) - but also negatively impact stability, all things equal.

FWIW, most experienced folks would really enjoy putting a 50mm rake fork on a frame like that for "everyman" bike rides that don't invovle 40kmh 70deg corners or 100kmh descents. Of course, ymmv.

ps: don't **** with a-c height.

[Keith A]

I've posted this on the forum a couple of times before...

I can say that a small difference in rake can make a big difference in the ride. I have a bike with a steepish HTA (nearly 74 deg) and it came a 43mm offset fork...and my initial rides on this were not favorable. So I swapped this out for a fork with a 40mm offset and it transformed the ride completely. I don't know if there was much of a difference between the A/C length, but I went from a Serotta F2 to a Serotta F3.

[Mark McM]

I noticed a difference in handling from the reduced trail when I went from a 42mm offset to 45mm.

Did you replace the entire fork, or did you alter the offset on the existing fork? If you changed the entire fork, how do you know the only difference was the offset? Several fork properties can influence handling, including the fork offset, height and flexibility.

[velomateo]

Thanks for all the feedback so far, I appreciate all the help. I measured the fork crown-axle length @ 370mm. The Ritchey Carbon, with the 43 rake has a crown-axle length of 368 - so it may be a good option.

@berserk87 Yes, these GT frames were Reynolds 853, the earlier versions were True Temper. Both of my GT's are of the Reynolds variety.

[Fivethumbs]

Did you replace the entire fork, or did you alter the offset on the existing fork? If you changed the entire fork, how do you know the only difference was the offset? Several fork properties can influence handling, including the fork offset, height and flexibility.

They were identical steel forks made for me by Della Santa with the only difference being the offset. I went back and forth between the two a few times and the 42mm with the 74 degree HTA felt better every time.

[velomateo]

I little update to this thread.

I finally mocked up the bike with the used Waterford fork I scored on Craigslist. Upon removing the old fork, I discovered that it has a data plate with the fork rake on it (40). The Waterford fork should be 45, according to their website. The crown to axel dimension is the same on both.

I haven't ridden the bike with the new fork, because it's not fully installed, so I don't know how it handles. Here's a few pics to compare, unfortunately the "before" pic isn't straight on - but hopefully it can provide a reference. Wheel base went from 98.5mm to 97.8mm.

What do you think?

Original Aluminum fork.
http://i238.photobucket.com/albums/ff297/velomateo/Saturn%20GT%20team%20bike/5D8B7BC4-1512-4E7F-B244-A306579C0ED1_zpsbshvkkj4.jpg (http://s238.photobucket.com/user/velomateo/media/Saturn%20GT%20team%20bike/5D8B7BC4-1512-4E7F-B244-A306579C0ED1_zpsbshvkkj4.jpg.html)

Waterford
http://i238.photobucket.com/albums/ff297/velomateo/Saturn%20GT%20team%20bike/8D739199-741C-4022-B97A-F9CCCFDE8FA5_zpsxjcdcrke.jpg (http://s238.photobucket.com/user/velomateo/media/Saturn%20GT%20team%20bike/8D739199-741C-4022-B97A-F9CCCFDE8FA5_zpsxjcdcrke.jpg.html)