Drive Side Down Stroke Flex Issue

[kingpin75s]

This is my first encounter with what I expect many people dealt with back in the heyday of CNC & SqT based on the threads I have reviewed. I believe my chain is rubbing my FD cage when I am standing or putting down heavy effort. Only occurs on the drive side downstroke.

Looking to see if there is a consensus on where to start for testing replacement parts.

1. Bottom Bracket
2. Crankset/Rings
3. The frame is just flexy and you are going to have to adjust around it, if possible

Details:

I am 145lbs and more of a spinner so this only happens really when standing or putting down heavy effort.

Frame is a 1995 Bontrager Road Lite.

Cranks are 1995 American Classic Stiff Arms and they are very light cranks. The Stiff Arm namesake could be a misnomer.

Rings are Race Face old stock 8 speed specific and are pretty solid.

BB is a Hadley Ti SqT 103mm JIS. Yes, Ti, but very short. Anybody at my weight tie back issues like this to strictly the Ti spindle?

Planning to swap a piece at a time and will likely start with moving the cranks to more of a known quantity with a forged Suntour XC Pro as I have one handy, but have ordered a steel BB as well. If I can swap the BB and keep these very cool and extremely rare cranks on the bike and working as they should, that would be my preference.

Curious with the details provided if anyone has experience or insight as to likely source or if combination of all things combined. Note this is not an invitation to talk about outboard BBs. My other dozen plus SqT setups are just fine, but they are all Stainless Phils so this is my first suspect outlier.

[ColonelJLloyd]

Different crank that uses outboard bearings can help, but much of the issue is the frame. I've had this issue on most older steel frames. I always assumed it was more likely to be an issue on larger frames (more leverage, likely a heavier rider) and I ride 62cm classic frames.

[robt57]

Put a steel BB in it...

8 speed D/A used a 103mm. a NOS one of those a good bet will fix you up.

You didn't say if you were using extended spindle or wide Q pedals...

[kingpin75s]

Put a steel BB in it...

8 speed D/A used a 103mm. a NOS one of those a good bet will fix you up.

You didn't say if you were using extended spindle or wide Q pedals...

Yeah. I would already have one to test if it didn't get destroyed when my post office was burned down this past month. Already have a Sugino steel on order as another 103mm D/A has not turned up at a reasonable price the past few weeks and my WTB post for a D/A or Phil here has not turned up anything either.

Definitely NOT using anything extended on the spindle end as purpose of these triple used as a double cranks and 103mm BB was to minimize Q-factor and optimize chain line. Current Q-factor is 147mm. I do run Frogs however as I need the full float and they may or may not be considered a wider Q pedal, but certainly no extenders.

[m_sasso]

I agree with robt57. I would begin with a steel spindle BB, when I was your weight the only BB's I ever had real problems with were flex-able Ti spindle BB's, broke two into pieces and that was enough for me.

[kingpin75s]

I agree with robt57. I would begin with a steel spindle BB, when I was your weight the only BB's I ever had real problems with were flex-able Ti spindle BB's, broke two into pieces and that was enough for me.

Thanks for the specific feedback on your weight and experience with Ti spindles. Maybe I should not have finally dabbed my feet into the Ti spindle game after decades of only running steel SqT.

Maybe I will just wait for the new Sugino BB to arrive as I really want to keep the current cranks anyway so will wait and start with BB and then address cranks only if I am forced to.

[ultraman6970]

All the squared tapper titanium campy BBs ive seen or are NOS or are cracked or straight broken at the driver side if I remember right. No idea about other brands.

[unterhausen]

I have used modern components on old steel frames and never had any problem with rubbing chains. I weigh quite a bit more than you.

If this is a new development, I would worry about a possibly cracked frame at the bb.

[Ozz]

All the squared tapper titanium campy BBs ive seen or are NOS or are cracked or straight broken at the driver side if I remember right. No idea about other brands.
I have a Phil Woods Ti BB on my Legend....I am at 185 lbs....running strong for 15 yrs....no flex that I can tell.

[ultraman6970]

There u have it... PW works fine.. .:D No experience with those ones... only knew campagnolo ones :P

[Peter P.]

..My other dozen plus SqT setups are just fine, but they are all Stainless Phils ...

I think you just answered your own question.

Since you have other bikes, you can swap another complete setup into the Bontrager to confirm it's not the frame but somewhere in the crankset.

I'd swap the BB first, perhaps with one of those Phil's. Unless the Ti BB is oversized inside the shell, the axle will flex more than a steel axle.

[kingpin75s]

I think you just answered your own question.

Since you have other bikes, you can swap another complete setup into the Bontrager to confirm it's not the frame but somewhere in the crankset.

I'd swap the BB first, perhaps with one of those Phil's. Unless the Ti BB is oversized inside the shell, the axle will flex more than a steel axle.

Fair and consistent with my direction, however I think people are underestimating the cranks in this equation. American Classic was always known for pushing the boundaries of weight and these cranks are seemingly no exception.

Do not feel like robbing a runner of the Phil for now but have a steel spindle on the way and will likely go that route as my first change mostly because I want to run the cranks. My take is it is both the BB and the cranks and that I will minimize flex by moving to the steel BB and that will be good enough.

Speaking of good enough, I did just retune my FD to push out my limit as far as I could without having a chance of outbound over shifting or my FD cage hitting the cranks. By offsetting my front cage to the outside I can still hit all 8 gears without rub and I can see the flex on my downstroke but it is no longer enough to rub.

Functionally there are no issues after this adjustment, however as someone who generally runs steel spindles and net forged cranks, this setup feels a little too weenie for me and I will likely be moving to a steel spindle regardless. Do not like seeing the visible flex.

I am sure I will do more testing as I have this recently NOS Hadley Ti BB which may just be a better combination with my Logic Compacts instead. Also have a NOS World Class Ti BB which like the Hadleys (and Phils) have good reputations. Hoping these Ti spindles test better with different cranks and that this was just a not so ideal double down on some weenie parts that were a potentially good match for the build.

Will provide feedback at some point once I test out some of these combinations.

[gbcoupe]

Fair and consistent with my direction, however I think people are underestimating the cranks in this equation. American Classic was always known for pushing the boundaries of weight and these cranks are seemingly no exception.

Do not feel like robbing a runner of the Phil for now but have a steel spindle on the way and will likely go that route as my first change mostly because I want to run the cranks. My take is it is both the BB and the cranks and that I will minimize flex by moving to the steel BB and that will be good enough.

Speaking of good enough, I did just retune my FD to push out my limit as far as I could without having a chance of outbound over shifting or my FD cage hitting the cranks. By offsetting my front cage to the outside I can still hit all 8 gears without rub and I can see the flex on my downstroke but it is no longer enough to rub.

Functionally there are no issues after this adjustment, however as someone who generally runs steel spindles and net forged cranks, this setup feels a little too weenie for me and I will likely be moving to a steel spindle regardless. Do not like seeing the visible flex.

I am sure I will do more testing as I have this recently NOS Hadley Ti BB which may just be a better combination with my Logic Compacts instead. Also have a NOS World Class Ti BB which like the Hadleys (and Phils) have good reputations. Hoping these Ti spindles test better with different cranks and that this was just a not so ideal double down on some weenie parts that were a potentially good match for the build.

Will provide feedback at some point once I test out some of these combinations.

FWIW, I had outboard bearings and a Sram Force crankset on this frame. No issues on shifting or flex. If anything, it was a little too stiff for my liking.

[oldpotatoe]

I believe my chain is rubbing my FD cage when I am standing or putting down heavy effort. Only occurs on the drive side downstroke.

Ya sure? Maybe adjust the front der outboard limit screw a wee bit? I am 60 pounds heaver than you and can't rub the chain on my front der on a ti frame.

BUT, I'd sure look at that before buying any stuff.

[oldpotatoe]

All the squared tapper titanium campy BBs ive seen or are NOS or are cracked or straight broken at the driver side if I remember right. No idea about other brands.

Type 1(hollow) but solid type 2, didn't break. I really doubt the OP, at 145 pounds is 'flexing' a titanium BB spindle..enough to rub the chain on the front der.

[David Kirk]

Like many above me have said - ditch the Ti spindle.

dave

[kingpin75s]

Ya sure? Maybe adjust the front der outboard limit screw a wee bit? I am 60 pounds heaver than you and can't rub the chain on my front der on a ti frame.

BUT, I'd sure look at that before buying any stuff.

Yes. I am sure it rubbed when I had the cage centered while in a middle gear as I usually set them up. You missed my update above where I did adjust my limit as you suggest:

"Speaking of good enough, I did just retune my FD to push out my limit as far as I could without having a chance of outbound over shifting or my FD cage hitting the cranks. By offsetting my front cage to the outside I can still hit all 8 gears without rub and I can see the flex on my downstroke but it is no longer enough to rub."

You can really see the flex just standing on the bike with the brakes engaged and putting weight on the drive side.

Really was never concerned about the frame, even though it was listed as a possible factor, but I believe the super light cranks just accentuate any concerns with the Ti BB.

Per recommendations and how delicate the current setup feels, I will be replacing the BB with steel and then will see if I am more comfortable with the cranks or whether it's time to swap them for a set of XC Pros.

[kingpin75s]

FWIW, I had outboard bearings and a Sram Force crankset on this frame. No issues on shifting or flex. If anything, it was a little too stiff for my liking.

Yeah. Have to list all possible factors, but I really did not think this had anything to do with the frame. Doubling down on a weight-weenie-esque crankset with a Ti spindle was clearly where I thought my issue was and I was curious as to how many people may attribute the issue to the 90s CNC cranks from a company known for pushing weight limits vs. the Ti spindle. This is clearly a spindle crowd but I do think it's a cumulative effect of the two pieces together. That's what I get for deviating from my normal bomb proof Phil Steel and XC Pros or Logics.

[kingpin75s]

Like many above me have said - ditch the Ti spindle.

dave

That is the plan. Replace the BB first with steel and if I still get more flex than I am comfortable with, I will ditch the cranks as well.

[dddd]

The crankarms are hardly even affecting the load path between the rings and frame, so likely not causing much flex there.

The "hub" area of the right arm is of course in the load path between the rings and the frame, but this area has more material cross-section and not much length as compared to the rest of the arm (which is not part of said load path).
The spider arms portion is within said load path but is not within the load path between the pedals and the frame, so there is no lateral loading on the spider other than due to chain tension (at it's greatest of course while cross-chaining).

Simply replacing the ti spindle with steel will reduce flex to near-abouts half of what the ti spindle allows...

[robt57]

I have a Phil Woods Ti BB on my Legend....I am at 185 lbs....running strong for 15 yrs....no flex that I can tell.

I have one SQ ti BB [109mm] in service for decades, and I am a Clyde. And was a lot more of a Cylde previously at times. ;O

With a good forged alloy chainset never had a flex issue that was untenable. Would I ever use a Topline, nope... To much girth, me obviously.

The tube wall thickness and grade of Ti used make all the difference in the world, yet we just say Ti BB. ;)

[dddd]

I would think that the design and tolerances of every part of one of these ti bb's could play into how well that the ends of the spindle were supported relative to the bb shell. Some gotta be better than others!

World Class made what was considered a good one back in the 90's.

I have one of those as factory-fitted to my Boulder Paris Roubaix F/S road bike.
But, in order to achieve a certain chainline with the Campag Racing Triple, they chose a 112mm JIS taper, which creaks like mad in the properly-torqued Racing Triple arms.
The pivot design of that bike forced them to use an unusually large chainline dimension, which was (bad) enough for me to move the 14t cog over to the inboard end of the cassette and then lock out that position with the lo-limit screw. Much more tolerable now as far as the cross chaining, but I still have to address the creaking!

Here is the offender, even has Ti spokes and Record-titanium cassette/hub and other bits. Was a pricey $4400 in it's day!
https://live.staticflickr.com/7068/6820080658_ac55f401de_c.jpg

I really need to re-evaluate the chainring gearing relative to the "stepped" profile of the frame/swingarm that the chainrings have to fit against. A compact double is what I hope to make fit there as the current 42t middle ring is almost touching the swingarm pivot, making a shorter spindle unworkable.
-

[kingpin75s]

Simply replacing the ti spindle with steel will reduce flex to near-abouts half of what the ti spindle allows...

That would make sense based on materials considerations alone. Certainly would reduce the movement I am seeing enough that I would not even have to significantly "tune" my FD a bit outboard to accommodate the movement.

[Tz779]

happened to me once. forgot to torque down the crank arm bolts.

[kingpin75s]

I have one SQ ti BB [109mm] in service for decades, and I am a Clyde. And was a lot more of a Cylde previously at times. ;O

With a good forged alloy chainset never had a flex issue that was untenable. Would I ever use a Topline, nope... To much girth, me obviously.

The tube wall thickness and grade of Ti used make all the difference in the world, yet we just say Ti BB. ;)

Appreciate this feedback as well. This thread certainly has me nervous about using my stock of Ti BBs under any conditions, but I was planning on testing with a good forged crankset as well. My 2 new steel 103mm BBs will arrive Monday so maybe I will test my Logics with my World Class Ti 103mm on my old Trek 613 this weekend.

Agreed all Ti BBs are not created equal and I was shooting for staying with brands I have seen good feedback on for the past 20 years or so by only considering Phil, Hadley and World Class.

[kingpin75s]

happened to me once. forgot to torque down the crank arm bolts.

Good thought, however should be set there. Torqued first to 24Nm as was playing it safe with light cranks then torqued to 28Nm after determining flex issue.

[kingpin75s]

I would think that the design and tolerances of every part of one of these ti bb's could pay into how well that the ends of the spindle were supported relative to the bb shell. Some gotta be better than others!

World Class made what was considered a good one back in the 90's.


Good to continue to hear solid feedback on the World Class ones IF I decide to use these in any manner. I have 1 Hadley and 2 NOS World Class ones that I will have to decide whether they get a home or go back in the bin.

[oldpotatoe]

Yes. I am sure it rubbed when I had the cage centered while in a middle gear as I usually set them up. You missed my update above where I did adjust my limit as you suggest:

"Speaking of good enough, I did just retune my FD to push out my limit as far as I could without having a chance of outbound over shifting or my FD cage hitting the cranks. By offsetting my front cage to the outside I can still hit all 8 gears without rub and I can see the flex on my downstroke but it is no longer enough to rub."

You can really see the flex just standing on the bike with the brakes engaged and putting weight on the drive side.

Really was never concerned about the frame, even though it was listed as a possible factor, but I believe the super light cranks just accentuate any concerns with the Ti BB.

Per recommendations and how delicate the current setup feels, I will be replacing the BB with steel and then will see if I am more comfortable with the cranks or whether it's time to swap them for a set of XC Pros.

You mean the 'bike shop' gig of standing next to the bike with the RH crank down and putting your fot on the outside of the pedal and pushing? And seeing all that 'flex'?
That's mostly frame and some tire movement you see.

May be the cranks..can you grab the RH arm when it's next to the RH chainstay and squeeze the crank arm and stay with your hand and make the arm touch the frame? If you can, it 'may' be the crank arm..

[Mark McM]

While the extra flex in the Ti BB doesn't help, I'm inclined to think that the rubbing is mostly caused by a combination of frame flex and front derailleur adjustment.

I'm just a little heavier they you, running about 150-155 lb, and I've been using Ti BB's for years. In my steel Ritchey Road Logic, I've used Erikson, Ritchey and Token Ti BBs in conjunction with Grafton SpeedStix cranks (these cranks are a little lighter than American Classic cranks). I haven't had a problem with chain rub. However, using similar Ti BB and cranks on a Litespeed Ghisallo (an ultra-light 900 gram titanium frame), I can get chain rub if I adjust the front derailleur in the normal way. But if I let out the deraileur limit stops on the Ghisallo, I can eliminate the derailleur rub. (This frame is very flexy, and when standing on the pedals you can literally see the seat tube bending in an between the derailleur clamp and the BB shell.)