Change to frame geometry with fork upgrade
 

Hello
I thought this would be simple but the more I learn the more confused I get.
I have a 60 cm stock bike from independent fabrications. I would like to upgrade from the stock fork.
However, the new Easton ec90 fork is different. It is 43mm rake, the original is 40mm. I'm not too worried about this, however the axle to crown height is also different. The new fork is 365 mm and old appears to be around 373mm.
I can see from the Sheldon Brown site that this will change me head tube angle .5 degrees approx. It is currently around 74.
What I cannot figure out is whether these two changes will cancel each other out or otherwise affect each other.
Any expert frame geometry advice would be amazing.

Just to make sure I have it right: original is 40mm/373mm; new would be 43mm/365mm.

In that case, both the shorter AtC and longer rake will decrease the trail. This will tend to make it easier to put the bike into a turn at speed, but it can feel unstable if overdone. The trail will be reduced form ~59mm to 53mm. Some people would say this is a lot, and some people (myself included) would say it doesn't make much difference and you can get used to it very quickly. It's still well within the range of "normal."

Of course, trail is not the only thing to worry about. For one, this will also affect front-to-back weight balance. Also, low speed handling is not all about trail. The steeper head angle can actually make it easier to keep the bike upright at low speeds.

As alluded to above, the effect of the 2 changes is additive, and will tend to make the bike handle faster. Too much "faster" can be twitchy. Whether the change is good or bad depends on whether you want it to handle faster, and your subjective impression.

Seems like a big change to me. I've had a bike with a 53mm trail and I was not a big fan; 59 to me, feels just right.

Why not track down an Alpha Q CS20 fork? 372 axle to crown and I believe a couple of offset options. under 350 grams, full carbon.

Hello thanks so much.
I just found a page on indyfabs website that said the stock frame had 55mm of trail at 60 cm. So I must have not measured the a-c too accurately. Will I still lose 6 mm? What do you think?
I live with a lot of hills so climbing is slow but descending might be shaky by your calculation?
One option I thought of was to try to get a headset with a taller crown race to compensate.. Would that help by bringing the head tube angle back? I know Chris king and cane creek both make tall crown races, only I would need a one inch...
What a pain.

Where do I get one of those? It's such a pain to find 1inch steerer carbon forks of good quality.......
Thanks!

http://www.amazon.com/Ritchey-Comp-R.../dp/B001CN6Q34

I got one on a bike I'm building up. Not the lightest, but still lighter than a steel fork.

Ebay has 1in carbon forks every now and then.

I didn't know you were looking for one inch. The Alpha Q came in 1" at one point but it'd be tough to find.

There are lots of alloy steerer options, Winwood, Performance, Ritchey.

May be just make friends with ebay?

The headset idea is a good one, but I think it'd be tough to make up more than 1-3mm.

I highly recommend not going with the EC90. The handling change will be drastic and for the worse. Yes its personnal preference, but I'm with Tri-Guy in that a bike with a 53mm trail is not nice to ride being horribly twitchy and it takes constant concentration of the road to ride no-handed (such as stretching and eating) because any little wheel wiggle and the bike wants to dive into that direction.

It's going to take some real searching to find something worthwhile and considered an upgrade, while still maintaining the handling. 1" fork options are now very limited, and in any size forks with low rakes are also limited.

Reynolds got out of forks
ITM - no 1"
Easton - Don't have the rakes
Enve/Edge - doesn't have the 1"
Pro-Lite - no 1"
Columbus Minimal - rake to big
Kinesis - makes lots of forks and lots of rakes. But most are cheap OEM-spec stuff and almost 600 grams. Is that really an upgrade?
Control Tech - wrong size and rake
3T - wrong size and rake

Some company may have made a 40mm or under rake fork in 1" long ago so it will take searching to find it.

Whoa - here it is!!! 1" steerer, 40mm rake, 400 grams, and Ouzo Pro was great fork!

http://cgi.ebay.com/Reynolds-Ouzo-Pr...#ht_500wt_1156

If 9" of steerer is enough, and maybe just with a 60cm frame, then this is seriously a perfect upgrade fork.

Ok, so Chris king has a plus 5 mm crown race/"baseplate". I think this would bring the head tube back up.
Not sure if this would help that much?

Here is another 1" fork thats quite nice:
http://store.repartocorse.com/shared...t=products.asp

p.s. looks like the chris king option only comes in 1 1/8 nd is not very elegant looking.