dbg

I dislike toe overlap but I seem to be on the borderline. 5'10.5" with ~31/32 inseam sometimes puts me comfortably on a 54cm bike depending on geometry --but 54 seems to be the crossover where toe overlap is common. My best fit is my 56cm CF roadie without any overlap (barely) but I have some 54 (seat tube) bikes where the top tube is too long (>57) for me.

I like to acquire frames and build them up myself, but at 54/55/56 sizes I'm taking a chance on discovering it ends up having toe overlap. I'm looking at doing some longer wheelbase builds (XC or touring frames) but want to know in advance if toe overlap will be an issue.

With the right measurements (wheelbase, chainstay, BB-drop, crank length, wheel diameter, tire size. shoe extension, etc) one should be able to predict it. I'm starting to try out measurements/calculations on my existing bikes (to see if calculations reflect reality) but was wondering if anyone else has tried this (calculating for toe overlap prior to a build).

stapfam

Toe overlap depends on the frame Geometry and build up of the frame. I only have one where overlap occurs and it never bothers me. That is Boreas with a 51 frame and Race Geometry. The Giant TCR at 51 does not have overlap and Neither does the Pinnie at 50. And neither did the OCR and that was a 49.

As I have said- Toe overlap does occur for me on Boreas- but only ever at slow speed and tight turns. Doesn't happen on every turn either and when it does- it does not bother me.

Shimagnolo

I was riding a bike for two years before I realized it had toe overlap, and that was only because I got curious and checked, due to a discussion in a thread here. So I regard it as a non-issue.

dbg

Turning around in tight quarters is where it happens. Never on the open road at speed. But in groups, at slow speeds, at starts and stops this becomes an annoying issue for me. And being clipped in makes it a problem. If i'm not clipped, then I just slide my foot out of the way. When you're clipped you can wedge the tire against the shoe and go down. Older bikes with long wheelbases don't usually have it. But modern road-ish geometries are much more likely to have toe overlap.

stapfam

While pedalling and turning the bars the wheel can touch the shoes- but as you continue pedalling- you go past that point and nothing happens.

DGlenday

This.

Which raises the question - why is toe overlap important to you?

I've always known I had toe overlap, and simply accommodate it when tooling around in the parking lot before a ride - which is the only time it is really apparent.

t4mv

^^^ x3

It's more important to have a bike with the correct ride & handling that you want (and therefore geometry) than it is to not have toe overlap. It may not be what you wanted to hear, but there it is, pick your poison.

stapfam

Just realised that when I am at slow speed and turning- I naturally point the toes down- hence taking them out of the wheels arc. Perhaps this is why I don't have the problem.

bruce19

When I first started riding those were exactly my dimensions and my 54 C to C road bike had exactly the same problem.

Doug64

My wife rides a 47cm frame with 700 c wheels. If anyone should have toe overlap issues it should be her. It has never been a problem, and I think she said the bike's odometer turned over 5500 miles (2 years of touring on it) the other day.

FWIW--I agree with the folks that maintain that there are other fit factors that are more important, but we all have our personal preferences.

It does not bother her a bit. She has ridden it in all kinds of conditions with out mishap. Well, at least not due to toe overlap She will even do a semi-track stand while waiting for traffic to clear when turning. This requires her to do a lot of movement with the front wheel and pedals to maintain balance at almost 0 MPH.

fietsbob

got the front to center, the BB to axle dimension? subtract crank length
and actual pedal axle to tip of toe clip.dimension..

then you have wheel radius coming back from Axle..

qcpmsame 

I've never had an issue with overlap and I have size 12 EEEE feet, wear 12-1/2 Adidas cycling shoes and I am not even close on my CAAD 10 or my R500. I do check this when I am shopping for an N+1. Just lucky I guess. Oh, my bikes are 56cm for the CAAD 10 and 58cm for the R500, 700C wheels on both with 23 width tires.

Bill

Garfield Cat

Here's a link to Cervelo's reply to toe overlap. Two things: no big deal, and how some other manufacturers deal with the issue.

https://cervelo.com/en_us/company/sup...sk-question/#3

Road Fan

It doesn't seem to me that the polite way to address a member's question is to show him his question is irrelevant either due to his misplaced values (more important fit factors) or his poor riding technique (you just move your foot through it or point your toe, or my wife can handle it, so it's not a problem). And at least get all the dimensions on the table: it's not just seat tube length, but at the same time angle, and BB height from the ground.

It can be affected by front wheel position, diameter, and presence/position/shape of a fender. Obviously this is all affected by head angle and fork offset, as well as top tube length and seat tube/saddle setback position. Also by crank length and Q-factor. Also by pedal design and foot position (related to toeclip length or cleat position, and whether you are pigeon-toed or not). Finally it's true that pedaling technique and cycling habits (never getting caught with the cranks horizontal) can affect whether it's a hazard when you have interference.

An overlap calculator involves every bike dimension except chainstay and seatstay lengths, essentially. It's not an easy equation to derive, and measuring bicycles accurately is not easy to do.

Given you can measure yourself and your bike accurately, it might be a lot easier to set it up on BikeCad and do a graphical study rather than a mathematical analysis. The need for accuracy is that a miss is as good as a mile, which makes it a game of millimeter accuracy.

ThermionicScott 

You make it sound as if the other posters were out to insult the OP, and I don't believe that's the case. Toe overlap is a common result of road bike geometry, and if it were more of a real-world problem, bikes would be built differently.

https://davesbikeblog.squarespace.com...o-problem.html

dbg

I actually was feeling mildly criticized for bringing up the topic. No biggie since 50+ is pretty civil. But I chose a topic to obsess over a little bit and to explore options because it does annoy me. Not helpful being told I should just deal with it. That's not why I brought it up. And bike builders DO address the issue and sometimes use smaller wheels on their smaller sized bikes. I'm now resolved to just explore it on my own.

Doug64

No criticism intended!!

qcpmsame 

dbg,
I thought it was an interesting topic, not one often discussed and pretty important to all of us. No criticism intended on my part towards you or anyone in the thread. Please keep the discussion going if you would.

Bill

dbg

You folks are so nice. How can I resist?

BluesDawg

It is probably possible to work out all the contributing factors and build a mathematical model to predict toe overlap, but it might be simpler, at least for popular bike models, to go to a manufacturer's forum like those on Mountain Bike Review and Road Bike Review and ask whether riders of the size bike under consideration have experienced toe overlap.

I've had a few bikes that had toe overlap, but my mad skillz prevent it being a problem.

dbg

If I adjust chainstay length down by 6mm (to account for ~70mm BB drop) and crank length down by same (to account for raising crank back above horizontal to intercept widest part of front wheel) then I can add:

(Adjusted chainstay value)+(adjusted crank length)+(toe extension past pedal center)+(front tire height)+(rim radius)

and should arrive at a value less than total wheelbase to insure no toe overlap.

Doing these measurements on 3 of my road bikes (one with a tiny overlap, one missing overlap by tiny amount, and one with no overlap by ~10mm) brings me to within 4 mm (short actually) of the theoretical model above.

For my values (170mm crank, size 10.5 shoe, 700 wheels) the calculation suggests wheelbase minus chainstay needs to exceed 600mm, while the measured bikes shows 587mm to be the magic value. The difference may be in the headtube angle and how it creates less than a perfect vertical pivot of the front wheel. I'm going to use 590mm as my magic value (wheelbase-chainstay) and see how that continues to work out on other bikes I measure or build.

dbg

First attempt done. Attaching gif. I'll have to figure out best way to make xls available for review

fietsbob

computer people... I just get out the tape measure on what I see in front of me..

qcpmsame 

I can't find any errors in your equation DBG, have you plugged any values in yet? BTW, very nice drawing and explanations for the variables/values, nicely done. I'd hope that TomD_77 sees this, his math skills are much better than mine are. Hope it works out, I'd like to use it if it works and I believe it will.

Bill

dbg

Attaching zip of actual working spreadsheet (does this work?)
toe-overlap-calc.zip