New Fork - Offset and Trail

Especially for light weight issues concerning cyclocross / touring bikes & parts.

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SgtRock
Posts: 29
Joined: Sat Mar 14, 2015 9:22 pm

by SgtRock

Hi

I have a Specialized Crux E5 fitted with a stock carbon fork which has a 45mm offset /rake. I am looking to upgrade this to something lighter & better and would like some advice about offset and trail etc. My frame is a 56cm with a 72 degree head tube.

I have looked at a few options and have narrowed down to TRP, Lynskey and Whiskey 9. Enve should be great, and I have one on my road bike, but can't justify the additional cost.

Anyway the Lynsey and the Whiskey 9 both have a 45 degree offset (same as stock fork) which gives a Trail of 66mm, a Flop of 20mm, and a Mechanical Trail of 63mm (based on 72 degree head angle and 35mm tyres).

The TRP has a 47 degree offset which gives a Trail of 64mm, a Flop of 19mm, and a Mechanical Trail of 61mm (based on 72 degree head angle and 35mm tyres).

All three forks have a crown to axle length of 397mm.

So I know that Trail, Flop etc. affects steering speed / response / stability but what does this mean in real life? The differences seem very small to me. Will I notice a positive or negative difference if I go for the TRP fork which has the bigger offset?

I am newish to cross racing and also ride the bike on the trails and through Jan and Feb it will be out on the road for the filthiest weather on road tyres.

My preference is for the TRP. It is the lightest, has internal routing, I can get it in any axle configuration but will probably go for through axle, it supports 160mm discs without an adaptor and it looks great, and it is the cheapest at £340 (Lynsey £380 and Whiskey 9 £430).

Thanks for any advice in advance.

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Calnago
Posts: 5635
Joined: Sun Nov 07, 2010 9:14 pm

by Calnago

I only got through half your post before I realized you don't understand what these things really are and in the process I learned that I have no idea that "flop" had a measurement. Offset is not measured in degrees. It is measured in Millimeters. And trail is trail, what do you mean when you say "mechanical trail"? It is simply a distance. As for "flop" please explain to me what you are referring to when you use that term. I know what I mean when I refer to "flop" in the context of handling characteristics but I have no idea how you would actually measure that. I'm curious.


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by Weenie


SgtRock
Posts: 29
Joined: Sat Mar 14, 2015 9:22 pm

by SgtRock

Ah Yes, offset in degrees was a slip of the keyboard. As for the rest, you have me bang to rights - clueless. Calculated the values using the following web tool: http://yojimg.net/bike/web_tools/trailcalc.php

I looked at their definitions, and in other places, but can't really get my head round it in simple terms. I am anticipating that the difference in handling between a 45 and 47mm fork will be nine tenths of bugger all but before investing a few hundred quid I want to be sure.

Does this help?

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Calnago
Posts: 5635
Joined: Sun Nov 07, 2010 9:14 pm

by Calnago

I would agree that you probably won't notice it in cross although I'd try to get the same offset as was on the original. I have never actually replaced a fork on the same frame with only a 2mm difference in offset and then test it to see if I could tell the difference. And in the wilds of cross I doubt you'd be able to tell at all. Someone else might be better able to help, but I wouldn't go less than what was on there before at 45mm. Your guess is as good as mine at this point. Just make sure the crown race etc is compatible with your frame.


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Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
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wheelsONfire
Posts: 1784
Joined: Mon Jul 07, 2014 8:15 am
Location: NorthEU

by wheelsONfire

I have changed forks on my Padauno racing (original monoque fork to Ax Lightness Helios), my Vial EVO D (ordered 3T team also) and the big change was my UP which went from 3T Luteus 2 to Lauf Grit.

* 3T Luteus, axle to crown 395mm, offset 50mm
* Lauf Grit, axle to crown 409mm, offset 47mm.
Actually less noted difference than i thought it would be.

The small offset you speak i doubt you will notice. Perhaps if a difference between forks lenght (axle to crown) and changing offset more than 5mm.
I understand that you think of this, but if you ask me, for this small difference it's not a problem at all.
Bikes:

Ax Lightness Vial EVO D
Paduano Racing Fidia
Open *UP*
https://opencycle.com/showcase/the-xplo ... eelsonfire

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