Q-factor - pedal strike calculator ?
 

I remember coming across an Excel form online where you filled certain measurements of your bike (BB height, Q-factor, pedal width) and it told you the angle of lean in which pedal strike happens.

Anybody have it bookmarked?

Back in the day we just leaned over the bike and watched for when the pedal touched the ground, then we "measured" the angle between the seat tube and the road. Andy (who has sharpened his Campy pedal quills with the road a few times)

I vaguely remember seeing something like that, but can't help you.

However, unless you're riding fixed wheel none of it matters.

Pedal strikes are easily avoided by good ingrained habits. Imposing limitations on bike design is unnecessary, and may cause other issues not justified by any actual benefit.

What would one do with this information? Use it for selecting bikes? Install an artificial horizon on the handlebars?

I doubt there is much variation between current road racing bikes.

My habits got ingrained in my racing days when I quickly figured out that with my poor sprint, I was much better off pedaling deeper into turns and sooner coming out. Loved my Fuji Pro with its near ridiculous 11" high BB that I had to really lean the bike to pedal strike with Campy NR style quills and 175 cranks. I've touched with my Mooney, same 175s and for the first decades, NR pedals a few times. (10-3/4" BB height.)

I call Peugeots and my Raleigh Competition "Slinkies" because the BBs are so low I hit pedals on a regular basis. Good thing is the lean angles are so low it isn't a big deal. But pedals that aren't rugged need not apply for work on those bikes. (I have a box of dead Leotard Berthet pedals - loose at the press-fits and missing all the dustcaps because the left ones want to unscrew every pedal strike. I don't know if pedal strike added to the press-fit loosening. It certainly did not help. Just saw that those pedals can be had on Ebay for $273. A higher BB and I could be wealthy.)

My idea is that this info would be useful for choosing cranks and pedals and if considering going down in wheel/tire size

EDIT: Found it! Right where I should have checked first, Sheldon Brown's site https://sheldonbrown.com/bbdrop.html

If I were going out to buy a stock $5000+ bike, I sure as heck would be looking at what does it cost me extra to have a bike I can lean like my Mooney before pedal strikes. The trends of the past decades to big Q-factors (chainlines creeping out, cranks going S-shaped, symmetrical BBs so all the stuff done to worsen pedal strike on the drive side is mirrored on the non-drive side) mean that it might cost me hundreds or even a thousand dollars to get the pedal strike down to what I've been riding since I took those clunky NRs off.

Aren't race bikes still tailored toward US criteriums (10-3/4"+ BBs) and European mountain races (closer to 10-1/2")? That 1/4" makes a big difference on pedal strike.

Q factor has got to be the least significant of the variables affecting lean limits. Surely crank length, bottom bracket height, even pedal platform width ... all of those probably 'can' have dimensional variables significant enough to affect lean angle. Cranks can be anything from 175mm (180mm) down to 140mm (130?). Could Q factor possibly have that kind of variability? Never mind, just opened the o.p. link in another window. A bottom bracket height calculator is a VERY different thing from a Q-factor calculator which even an outlier geek like SB knew wasn't worth getting hot and bothered about.

I just sketched out a typical road bike. Angular effects of changing BB height, Q-factor and crank length are:

B Height, 1/2" (12.5 mm) change - 3.6 degrees or 3.5 mm change causes 1 degree of lean
Q-factor, 30 mm change - 2.2 degrees or 17 mm change causes 1 degree of lean
Crank arm length, 20 mm change - 3.8 degrees or 3.5 mm change causes 1 degree of lean

Pedals can make a much bigger impact.

I drew this around a 10-3/4" BB height varying:

B Height, 11" to 10-1/2"
Q-factor, 135 to 175 mm
Crank arm length, 180 to 160 mm

Pedal used was a Shimano Dura Ace semi-platform that measured 3-1/2" width along the spindle centerline and is so cutaway that I assumed there would be no hit first from a bottom corner. (The pedals are designed for racing on the velodrome where pedal strikes are crashes,)

Well, we do not disagree. But my point really was: does the Q-factor even have extremes as wide as for other components? I don't think it does. I think the Q-factor of the average track or 1x road bike, all the way up to a cargo bike triple might be 25mm (1") and not much more? Bottom bracket drops between bike classes can be 2" or more, and crank lengths can vary 4" at the extremes, but most commonly sit around 160mm to 175mm. Pedals can vary from clipless that are narrower than the shoes they attach to, up to the platform monsters that are wider than a EEE shoe. If there was something you wanted to measure to see how far you could lean over, the Q-factor dimension would not be the first one to be investigated I don't think. The exact contrary actually. Full disclosure: Thanks to FAT and E-Bikes, outlier Q-factors are being seen more often. Given that I've heard so many complaints about "normal" Q-factor dimensions I have to wonder who rides the bikes with the 246mm Q-factors?

None of these things has extremes. Today's bikes and cranks are more alike than different. You can't even use a modern derailleur with a Nuovo Record era crank because the arm is too close to the outer chainring.

Current aftermarket cranks are poor matches to Shimano and Campy front shifting, even if you can find a usefully narrower one.

So I don't see what anyone hopes to get out of this aside from being nostalgic to the days of narrow cranks and actual crit geometry.

I would think Q factor and crank length would be best determined by fit rather than pedal strike. Otherwise just ride the shortest cranks with the narrowest Q factor that you can stand. Roads are not level anyway and humans are not super accurately consistent, so I'm not sure knowing a precise number would be of practical use anyway. I like Kontact 's idea of an artificial horizon, but chances are you need to be looking where you're headed and not at your handlebar if you're cornering that aggressively.

I think you’re way overthinking this…..🤔

For context, I'm converting a French tourer (notorious for low BB's) from 700C to 650B and planning to use these. Cranks are narrow Q though.

https://cimg5.ibsrv.net/gimg/bikefor...6ae400aef7.jpg

You can always do what the motorcycle racers do: lean slightly to the inside of the curve, causing the bike to be more upright. No need to drag yur knee though! :innocent:

You're taking a bike with a low BB and making it even lower? :foo:
Crit racers do that as well.

You can even do this quite a bit. I rode my Peugeot UO-8 for years fixed and got really good at the "lean away". Drawback was real understeer. The lean away was basically telling the bike to go straight and you had to physically make it turn with your hands. But it sure beat hitting the pedals and rapidly destroying them.

Did similar with the UO-8 of my last post. Removed the 27" wheels and went tubular/sewups. Dropped the BB a lot from already low.

Pedal strike is only a consideration if you need to pedal through corners at high speeds. Only bike racers need to pedal through corners. Everyone else can coast.

Assuming your "old French tourer" is not going to be used for racing, which seems a fair assumption, maybe just consider coasting through corners.

Should have had a Raleigh Pro.

Don't know if the o.p. is having us on or not with the plan to use Juvenile Market pedals, but, usually, a change to 650B also involves enough of an increase in the new tire's radius that bottom bracket height remains more or less the same as before. Otherwise, why bother??