Need a new fork?

[Johnny P]

My current bike is a 2001 Merlin Extralight. It fits me well and rides fine, except I would like more stability on downhills. I am considering replacing the fork to gain this stability. Right now I have an Easton EC90 superlite with 43 mm of rake. Would changing the fork give me what I'm looking for? Would changing the fork rake help? Would a Serotta fork help? I would appreciate hearing what you think. :)

[Serotta PETE]

Johnny, I would send a note to Tom K at Spectrum (or give him a call) He would be your expert in this area for no one knows Merlin better than he.

PETE

[Tom Kellogg]

Johnny:

The rake that is best suited to that frame depends on the frame size. Merlin Extralights use 50s,45s, 43s and 40s depending on the head angle, and the head angle depends on the frame size. If you know the head angle of your frame you will be good to go, but if not, look it up on the Merlin web site. It works like this:
head angle Rake
72.5 50
73 45
73.5 43
74 40

The other issue is the lateral and torsional stiffness of the fork. Easton SL forks are pretty stiff longitudinally, but not torsionally and in fact, the SLX is laterally very soft as well. I would look at the Reynolds Ouzo Pro, Ultra Light, or Ouzo Comp. The Alpha-Qs are excellent forks, but they come in 41 and 44 rake only. That is OK, but with them you can't quite get a dead neutral rake. Wound-UP forks are amazingly stiff torsionally and quite stiff laterally. As long as you like the way they look, they are a good choice. The Serotta carbon forks are in the absolute top ranks of forks as well. They are made in the old Reynolds facility in southern California where Serotta can keep a close eye on every aspect of their manufacture. Good luck.

[Louis]

but they come in 41 and 44 rake only. That is OK, but with them you can't quite get a dead neutral rake.

Tom,

When you say "dead neutral rake" does that imply that your goal is a certain range of trail for a given frame's intended use? (By intended use I mean a touring vs. club ride vs. stage race type of thing.)

Thanks
Louis

[RPS]

....snipped..... I would appreciate hearing what you think. :)Have you excluded other factors besides the fork? Some variables like wheels are so easy to check that it’s worth considering if you haven’t done so already.

I ask only because your post reminded me of a conversation I had with one of the best builders around who told me that he often sold super light frames and forks to riders who wanted to build a super light rig, so they’d use super light “everything” (i.e. -- components, bars, stems, wheels and tires) and then they’d come back to him because the bike felt wrong, even though the frame itself was actually stiffer than the original it replaced.

I’m not suggesting you have a similar case, just that it may be prudent (from cost standpoint) to rule out other factors if possible.

FYI: My Easton EC90 was fine for me, but I’m not all that heavy. It isn’t really stiff, but I liked it enough to buy another one.

[Johnny P]

Here's the rest of the story on my Merlin. I bought it in 2001 but had to send it back under warranty at then end of 2003 to replace the head tube which was ovalized. According to the 2003 Merlin spec sheet, my frame size should have a 73.5 degree head tube angle and a 73 degree seat tube angle. I just measured both and the seat tube angle is 73 degrees, but the head tube angle is 75 degrees. This could explain the problem. I guess the best I could do is get a 40 cm rake fork to fix this situation (or a new bike).

[bluto]

JP; If you are interested in selling the EC90 how much of the steerer tube is left?

I have a Reynolds Ouzo Pro with 40mm rake and would offer trade +/- money if you are at all interested........

But to be honest i'm still waiting to see what TK's response will be to Louis' question since i'm not sure what size fork I need. :confused:

[Samster]

I just measured both and the seat tube angle is 73 degrees, but the head tube angle is 75 degrees.i'm no frame builder but that's awfully steep for a head tube. how did you measure that? did you use a level? some top tubes slope ever so slightly (my 51cm st Pegoretti does this) that you have to take this into account before you apply the "protractor." unless you're really tall, i don't know of many road bikes that have that kind of front end... assuming you want about 6 cm of trail, you'll need 30mm of rake. 40mm of rake will only get you 5.0 cm of trail (more like a track bike.) at your current 43mm of rake, you're getting about 4.7 cm of trail (less than some track bikes!). that's all assuming your total wheel diameter (w/ tire) is 68cm and your head angle measurment is right. try this link (http://www.kreuzotter.de/english/elenk.htm). good luck...

[Tom Kellogg]

Johnny:

Dead neutral for me means that the trail allows the bike to head where you aim it without "having a mind of its own." In a fast sweeper, the bike should have no tendency to either climb out or dive into a turn. It should be "neutral." The trail number that works, assuming 23mm or smaller tires (700-C) and a reasonable fore-aft center of gravity is 56-57mm. This also assumes that there is no extra weight carried on either the bars or the fork.

As far as the new head angle goes, YIKES! How much different did the bike feel when you got it back from Merlin? It should have understeered like crazy. I think that you should have the "new" head angle confirmed by someone with a frame jig who can really check. Finally, if the head angle really is 75, either have it reduced with a new head tube or try to find a 38mm rake fork.

[Samster]

if the head angle really is 75, either have it reduced with a new head tube or try to find a 38mm rake fork.i defer to the master...

[Louis]

The trail number that works, assuming 23mm or smaller tires (700-C) and a reasonable fore-aft center of gravity is 56-57mm.

Thanks Tom, this is very useful information.

Louis

[vaxn8r]

TK, I heart your posts. I learn a ton reading them. Thanks!

[Johnny P]

Thanks for all of the advice. I'll check with a LBS to see if I can get a more accurate measure of the head tube angle and proceed from there.

I had the warranty work done over the winter and when I got the frame back I switched to a different gruppo (from Shimano to Campy which meant new wheels) plus I needed to buy a new fork since the new head tube was longer than the old one. With all these changes, it's hard for me to compare pre and post warranty ride quality.

One more question, would changing to a 38 mm fork from the current 43 mm result in more or less toe overlap?

Thanks again,
JP

[stevep]

my opinion.
they botched the repair.
get an accurate measure and them make ( those idiots ) fix the thing correctly- or give you a new frame- if the head angle is that far off due to a repair that they did.

[Tom Kellogg]

One more question, would changing to a 38 mm fork from the current 43 mm result in more or less toe overlap?JP

...that would be 5mm more toe overlap.

[michael white]

but the overlap is, if you ask me, inconsequential compared to how well the bike rides.

I have a Cyrene which handles fine and dandy. When I bought it, I believe the factory chart called for 40 rake on a 73.5 hta, for the 55. It came with a 43. I was a stickler for the factory specs, and changed out for the 40. The dealer told me it would overlap, and I said I didn't care. I don't know if the charts are the same now, if they changed, if the models were spec'd differently, or maybe I misread the chart back then.

Now, judging from what Tom is saying, maybe conventional Merlin thinking, at least for the Ultralight, which is, admittedly, a slightly more racy frame than the Cyrene, would have me riding slightly less trail. But I like the 40. I ride no hands no problem.

I have a 43 I might try someday, but I don't see why.

A roundabout way of saying, shoe rub might be slightly unsightly for the shoe, but that's pretty much all there is to it.

mw