Cycling UK Forum

Hi, will measure tomorrow and advise, thanks.

Front centre as accurately as I can :
Ribble CGR Ti 595mm
Dawes Super Galaxy 625mm
Sonder Broken Road 705mm

MIB2020 wrote:Front centre as accurately as I can :
Ribble CGR Ti 595mm

You have not told us what the frame size is.

Small as advised by the Ribble team , Sonder is medium and Dawes I think is 53/54 ?

Spa Roughstuff 53cm, 640mm front centre
Wayfarer 54cm, 635mm front centre
Both the above 2 bikes designed for drop bars
The Sonder seems to be a flat bar (mountain) bike; this makes it easier to get good toe clearance without excessive reach.
The Spa Roughstuff is one of my early designs, and has a long reach for a drop bar....it was OK for me when i could still use drops, but realistically too long for some
Roughstuff 001 by 531colin, on Flickr
Wearing Nitto Noodle bars, which I liked for their long ramps.

That looks lovely, probably more like the bike I should have bought. I notice the forks are curved, this I think extends the length, what would happen if I fitted similar to the Ribble ?

I expect others will be able to comment more knowledgeably, but I think if you compare your frame with similar bikes from other brands you will find the front centre measurements are very similar, and certainly none of them will be anything near 50mm greater.

Simply put, small frame + 700C wheels + 40mm or larger tyres + mudguards + offsets generally available on carbon forks = difficult/impossible to design without overlap, and there is no single magic bullet fix. For example, switching to 650B wheels but with 47mm-50mm tyres to compensate for the reduction in tyre volume would give you ~10mm. If you have 20mm or more of spacers under your stem, you might be able to get away with a medium size frame, and it looks like that would give another ~5mm based on the difference between Ribble's wheelbase measurements.

However, if you want a lot less toe overlap than you currently have, then that really needed to be one of your criteria when choosing your bike, and that would mean knowing the front centre measurement (or using Pythagoras to calculate it from the wheelbase, bottom bracket drop and chain stay length and then verifying the actual measurement of any bike on your final shortlist).

My guess is that Spa's Elan probably has amongst the largest front centre measurements of bikes in that class, because it was designed by 531Colin on here, and - as he has made clear in many posts - toe overlap/mudguard clearance are important to him. It's no coincidence that Spa actually provide the front centre measurements for their frames, unlike most other brands.

Edit - Crossposted with 531Colin's post above.

Thanks slowster, annoying Ribble, who could tell I was a newbie to road type bikes by the questions I asked , never mentioned this. Let’s hope their customer service do there job or I may be advertising the bike on here for sale.
Worse things can happen, I will ask the wife if i can order a Spa prior to the return/sale of the Ribble

slowster wrote:
My guess is that Spa's Elan probably has amongst the largest front centre measurements of bikes in that class, because it was designed by 531Colin on here, and - as he has made clear in many posts - toe overlap/mudguard clearance are important to him. It's no coincidence that Spa actually provide the front centre measurements for their frames, unlike most other brands.

However, I test rode a Spa Elan Ti in 2017 and one of my few complaints about it was the toe overlap!

viewtopic.php?f=18&t=113400&p=1113853&hilit=Spa+Elan#p1113853

rotavator wrote:

slowster wrote:
My guess is that Spa's Elan probably has amongst the largest front centre measurements of bikes in that class, because it was designed by 531Colin on here, and - as he has made clear in many posts - toe overlap/mudguard clearance are important to him. It's no coincidence that Spa actually provide the front centre measurements for their frames, unlike most other brands.

However, I test rode a Spa Elan Ti in 2017 and one of my few complaints about it was the toe overlap!

viewtopic.php?f=18&t=113400&p=1113853&hilit=Spa+Elan#p1113853

Bikes like the Ribble and the Elan are constrained in their front geometry by the offsets that are available on carbon forks. As 531Colin posted on your thread:

531colin wrote:Fair enough.....front centre on the 54 is 615mm
With a 37 x 622 tyre and mudguard clearance its going to be tight.
If i could get forks with anything more than 45mm offset I could have a slack head angle which gives a short reach to the bars and a decent front centre, but as it is its a case of "short reach and toe clearance....choose one."

Well OK, but caveat emptor....

rotavator wrote:Well OK, but caveat emptor....

Indeed....but before the buyer can beware, he needs to be informed.
Spa publish geometry data which includes front centre, and encourage proper test rides. I make that Spa 2, Ribble nil?

Going back to the previous thread, you said you tested a 54 Elan, and your shoes are size 10 1/2 ?
As it happens, I ride a 54 and my shoe size is 7.
I'm just a bike designer, I haven't got any magic to circumvent the laws of physics, I'll have to leave that to the really clever people.
If you have big feet, and you want mudguards but not toe overlap, and you insist on using carbon forks and 700c wheels with sensible size tyres, you are going to have to accept a compromise somewhere.
Carbon forks are only available to me in a very restricted range of offsets; thats 45mm or 50 at a push. So if I want the bike to steer properly I can either sprinkle some fairy dust or stick to a head angle not too far away from 72 degrees. So if you want a lot of toe room you are going to have to accept either a short stem or a long reach (or flat bars, etc.) Thats the sort of thing you can decide on an individual basis, but its not something I'm going to wish on everybody else who happens to want the same size in an off the peg bike.

If you don't insist on a carbon fork, I can have any sensible offset I like.
Thats why the bikes designed around steel forks have more toe clearance.
54 Elan.....615 front centre (56 & 58 are 620 & 630 respectively)
53 Roughstuff..640 front centre
54 Wayfarer...635 front centre
OPs Ribble...595 front centre

Hi Colin
So is it possible to fit a titanium fork with a bigger offset without ruining the bike ?

I was writing this yesterday(?) then my PC went down.....

MIB2020 wrote:That looks lovely, probably more like the bike I should have bought. I notice the forks are curved, this I think extends the length, what would happen if I fitted similar to the Ribble ?

Fork blades can be straight, but angled forward from the crown, or they can be bent forward as traditional steel fork blades are.......it doesn't matter how you do it, offset is offset, and the fork offset is an essential part of the design of the bike steering....the other bit is head angle https://en.wikipedia.org/wiki/Bicycle_and_motorcycle_geometry.
If you fit a longer offset fork and keep the existing head angle, your steering will get twitchier. You can pair a longer offset fork with a slacker head angle....either use a fork which is longer (axle to crown race seat) to jack up the front of the bike, or use the same length fork and that headset which gives you some head angle adjustability which somebody linked earlier. (NB...integrated or not?)
Previously, I said the Roughstuff was an early design, and I simply made the frame longer (than the Tourer) to get more toe clearance.
The Wayfarer is more recent, and I used longer offset forks and a slacker head angle to get toe clearance without excessive reach.
Its moderately complicated to work out exactly what front centre you would end up with when altering both offset and head angle (via longer fork or adjustable headset; I think you would need a Bike CAD system , for example Bicycle Forest.(I'm afraid I can't help with CAD, its too hard for me!)
Some suitable numbers.....
71 deg 54mm offset
70.5 deg. 59mm offset

Thanks Colin, I understand the basics, perhaps if Ribble refuse a refund they could at least offer the design of forks to assist me. I do like the sound of a twitchy front end , I am somewhat used to that with various motorcycles I have ridden over the years.
It’s again beginning to sound like selling the bike is the easiest option, they are in great demand, end of May is earliest delivery for new and ensure my next one gives good clearance.