Have a late 80's Battaglin - I like the bike and really have no desire to change. Have a lot of miles on it. However it is very "twitchy". You cannot take both hands off the bars - period. Above 30 mph - you have to pay attention - above 35, it's no fun @ all.

It has a 75° HTA, and (about) 47mm rake/fork offset and trail of about 40mm. 700c x 25mm with quite a bit of wear.

So my question is - if I put a fork in it with - say 43-44mm of rake that should get my trail up to 45mm or so. Will that 5mm be enough to take some of the abruptness out of the bike with a 75° HTA?

I primarily ride pleasure/recreation. Rode just over 3000 miles last year.

marc

I have tried to understand the pros and cons of more vs less trail and it still confuses me. I am too interested to see what others have to say.

From what I understand less trail translates to twitch ride at slow speeds and easy turning at high speeds. More trails translates to steady ride at slow speeds and hard to turn at high speeds. I think it all has to do with how quick the front wheel turns when the bike is tilted.

I don't know what you guys are talking about but I also have some high speed twitching. During my ride I reached 40mph coming down a mountain and there were some times when I felt the front wheel twitching, got kinda scary but it was still fun .

What I'm trying to say is that I'm attaching myself to this thread in order to to learn something.

If it can take wider tires, that's one way to increase trail. Put the biggest one you can.

Use this handy dandy calculator: https://yojimg.net/bike/web_tools/trailcalc.php

Trail around 5.4 to 6.1cm is where it's at, yo.

Problem Solved.

Somebody, I think it's Cane Creek, has started making an offset headset for mountain bikes which can change the angle by a full degree. I don't know if they have anything that will work with a quill set-up, or if you can convert to threadless and make something yourself. Just a thought.
I like the steep angle myself.

What you're likely talking about is the high speed wobbles, which is a different issue from how the bike wants to turn.

Short answer to your problem is put a knee to the top tube when it happens. Long answer is read some of the threads on high speed wobs.

Well, my bike has trail of 56mm and it definitely doesn't feel relaxed, and it handles very well at speed in crits. I thought about moving to 60mm trail and someone said I would be able to detect the change at the margins, just not a lot. If you've got you're measurements right, and there's no toe overlap issue, I think you could go with even less rake (I think Edge makes one, but not cheap).

You might be better off going to a custom guy (like Bilenky in Philly) and having him make you a nice chromed steel fork so you could get exactly the trail you want. Probably not that much more expensive than buying a new carbon fork and it'll look so much better on your bike.

Every little bit will help, however, 75deg HTA is like that of a track bike; those usually have forks with about 30-35mm offset. 60mm trail is considered by framebuilders to be more or less neutral as far as the balance between responsiveness and stability; most racing frames are built a bit short of this to make them a bit quicker handling. 57mm is pretty common on both road (73deg, 43mm offset) and track (74.5deg, 35mm offset) bikes.

In the early days of cycling, bikes were designed with no trail as it was believed that the wheel "flop" (the need to lift the mass of the bike to straighten out the wheel) made the bike sluggish. Then, gradually trail was introduced as bikes got lighter (negating the effects of wheel flop) and people realized that steering stability came with increasing trail. I read somewhere that early "modern" italian bikes, which is what you have, were sometimes built to be very twitchy.

A good primer on trail, though oriented to track bikes is here.