Changing fork rake to address toe overlap?

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iamraymond
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by iamraymond

I know I know I know.... toe overlap is a problem with the rider not the bicycle and I should just get used to it.

One of my bikes (2016 Litespeed T7) has terrible toe overlap compared to my other bikes. It is a size small (50cm) and has a 72.5 HTA paired with an Enve 2.0 fork with 43mm rake. I've already switched from 170mm to 165mm cranks and use my narrowest shoes when riding this bike. But I'm still experiencing overlap. I already had a close call while climbing really steep switch backs. I typically ride the longer, less steep line around the curve, but if a car is descending then I'm forced onto the steeper inside line which requires turning the front wheel. A small touch of the front tire while going full gas off the saddle can lead to a crash.

So I am thinking to replace this with a fork with 50mm rake. What I've seen from bike builders (like Pegoretti) they fit 50mm rake forks on frames 53cm and smaller and a 45mm rake for larger frames. This should push the front wheel forward a bit, but I don't know if it's enough to make enough of a difference. I know that this change will make the bike more twitchy, but I should be able to get adapted to it.

Any thoughts on this change? Would a 7mm change in offset make enough of a difference?

jih
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by jih

I don't know how this change would impact geometry, but if the issue is only rocking and turning the bike while climbing steep hills, maybe lower gearing could help?

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iamraymond
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by iamraymond

jih wrote:
Fri Mar 17, 2023 10:03 am
I don't know how this change would impact geometry, but if the issue is only rocking and turning the bike while climbing steep hills, maybe lower gearing could help?
Yes it will certainly affect how the bike feels. I'm already running a 50/34 with an 11/34 cassette, but some of those turns are >20% if you're forced on the inside line.
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BdaGhisallo
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by BdaGhisallo

How do you find the handling now? Putting on a fork with more rake is going to make the steering more twitchy.

gorkypl
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by gorkypl

Search for fork rake calculator online and enter the desired values, you will see the resulting trail. For a road bike, 72.5 HTA with 50mm rake will put you into low-medium trail, so you can expect much faster, twitcher reaction from the bike - 7mm is a lot. For me it would be too fast steering with narrow tyres, but it's a personal preference.

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ultimobici
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by ultimobici

gorkypl wrote:
Fri Mar 17, 2023 11:13 am
Search for fork rake calculator online and enter the desired values, you will see the resulting trail. For a road bike, 72.5 HTA with 50mm rake will put you into low-medium trail, so you can expect much faster, twitcher reaction from the bike - 7mm is a lot. For me it would be too fast steering with narrow tyres, but it's a personal preference.
Try https://bikegeocalc.com/

That way you can see both the change to the front centre measurement as well as the change in trail. 72.5º is on the steep side for a frame as small as you have.

iamraymond
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by iamraymond

BdaGhisallo wrote:
Fri Mar 17, 2023 10:57 am
How do you find the handling now? Putting on a fork with more rake is going to make the steering more twitchy.
Yes I understand this will happen, but I think I could get adjusted to the handling. I'm just more concerned that the 7mm won't make much of a difference in the toe overlap.
ultimobici wrote:
Fri Mar 17, 2023 11:19 am
Try https://bikegeocalc.com/

That way you can see both the change to the front centre measurement as well as the change in trail. 72.5º is on the steep side for a frame as small as you have.
Thanks. I played around with this tool and the 50mm does move it forward but it’s hard to tell if it will be enough to eliminate the overlap. Yes you’re right the HTA on this frame is quite steep compared to my other bikes at 72, 71.5, 70.9. I’m no geometry guru but I imagine this is why this frame has so much overlap compared to my other bikes.

jih
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by jih

iamraymond wrote:
Fri Mar 17, 2023 10:23 am
jih wrote:
Fri Mar 17, 2023 10:03 am
I don't know how this change would impact geometry, but if the issue is only rocking and turning the bike while climbing steep hills, maybe lower gearing could help?
Yes it will certainly affect how the bike feels. I'm already running a 50/34 with an 11/34 cassette, but some of those turns are >20% if you're forced on the inside line.
Yeah, that's already about about as low as gearing gets on a road bike without sacrificing top-end speed, or switching to a system that starts with a 10t sprocket.

Are you moving from side to side up the ramp effectively to make it less steep?

jfranci3
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by jfranci3

What tire size? A fork is $600?
-angle headset might give you 10mm more for $200
-eccentric bottom bracket 6mm for $175
-650b wheels / tires- 20mm for $xxxx
Last edited by jfranci3 on Fri Mar 17, 2023 1:53 pm, edited 1 time in total.

iamraymond
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by iamraymond

jih wrote:
Fri Mar 17, 2023 11:53 am
Are you moving from side to side up the ramp effectively to make it less steep?
No I don't find myself zig zagging up the climbs. I find that a bit unsafe on steep, narrow roads. I could see that being a problem for someone with overlap.

DaveS
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by DaveS

Toe overlap should only be a concern when making a u-turn at very low speed. I stop pedaling in a tight u-turn at the half way point of my out and back routes. At normal speeds, the tire should never turn far enough to create toe overlap.

IvanZg
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by IvanZg

Place your shoes on the pedals and simulate situation where you overlap with the wheel and see if 7mm will be enough

iamraymond
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by iamraymond

jfranci3 wrote:
Fri Mar 17, 2023 1:40 pm
What tire size? A fork is $600?
-angle headset might give you 5mm more for $200
-eccentric bottom bracket 6mm for $175
-650b wheels / tires- 20mm for $xxxx
Thanks for those options. I'm using 28mm tires, but I just purchased a set of 25mm to see if that will help. The fork is more like $300.

I've never considered an angle headset or eccentric BB. I need to read more about that.

jih
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Joined: Fri Jan 29, 2016 12:54 pm

by jih

iamraymond wrote:
Fri Mar 17, 2023 1:45 pm
jih wrote:
Fri Mar 17, 2023 11:53 am
Are you moving from side to side up the ramp effectively to make it less steep?
No I don't find myself zig zagging up the climbs. I find that a bit unsafe on steep, narrow roads. I could see that being a problem for someone with overlap.
You should have to be turning quite sharply before you get toe overlap then - basically a u-turn. Are the vehicles coming the other way taking up most of your lane too, so you're left making an extremely tight bend?

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jfranci3
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by jfranci3

iamraymond wrote:
Fri Mar 17, 2023 1:55 pm
jfranci3 wrote:
Fri Mar 17, 2023 1:40 pm
What tire size? A fork is $600?
-angle headset might give you 5mm more for $200
-eccentric bottom bracket 6mm for $175
-650b wheels / tires- 20mm for $xxxx
Thanks for those options. I'm using 28mm tires, but I just purchased a set of 25mm to see if that will help. The fork is more like $300.

I've never considered an angle headset or eccentric BB. I need to read more about that.
I woudn't tolerate any toe overlap with a road tire. On a softer tire, you can just power the tire past the rub, but a road tire has no where to go and the risk is higher.

If you're 2x in front, I'd do the angle headset before the BB. At $300, I'd still do the headset first. The fork offset will give you less trail (stability), the headset will give you more stablity. I wouldn't worry about the handling too much as you're not changing the chainstay length, so you won't change your percieved handling. You are changing the wheelbase in any case, so that will impact your extreme low speed handling (basically, your turn radius).
Did you measure the overlap?
Do you know the direction of the offset with the fork mounted? I doubt you get all 7mm, it proabably nets out to 6mm with the rake depending how they measure it, so I wouldn't cut it close.

What wheels are you running? If you go wider internal, it'll oval out a tire a bit, so that'd give you 1-2mm. Maybe borrow a wide rim from someone to try that.
Last edited by jfranci3 on Fri Mar 17, 2023 3:12 pm, edited 2 times in total.

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