Lugged chain stay maximums

[baldbones]

Apart from Max B.B. shells what are the largest chain stays you can fit in a lugged bottom bracket. I hesitate to say stiff but hopefully you know what I mean..
Are Sax Max ones any larger?
I know fillet gives you more choice but I just love lugs
Just curious and can’t figure out an answer on Ceeway/ Nova etc
Thanks
Rick

[bicycletricycle]

Originally Posted by baldbones

Apart from Max B.B. shells what are the largest chain stays you can fit in a lugged bottom bracket. I hesitate to say stiff but hopefully you know what I mean..
Are Sax Max ones any larger?
I know fillet gives you more choice but I just love lugs
Just curious and can’t figure out an answer on Ceeway/ Nova etc
Thanks
Rick

MAX are the biggest lugged stays ever made?

[David Kirk]

Originally Posted by baldbones

Apart from Max B.B. shells what are the largest chain stays you can fit in a lugged bottom bracket. I hesitate to say stiff but hopefully you know what I mean..
Are Sax Max ones any larger?
I know fillet gives you more choice but I just love lugs
Just curious and can’t figure out an answer on Ceeway/ Nova etc
Thanks
Rick

Hmmm?

Do you mean what are the largest diameter c-stays that can fit into a lugged BB shell?......or are you asking what are the stiffest c-stays that can be used in a lugged BB shell?

They are not the same thing.

dave

[baldbones]

I guess I’m asking stiffest..

I suppose I thought that as Max were pretty big and are often cited as stiff(and from my own experience too stiff for me) that bigger was stiffer.

Thanks

[David Kirk]

Originally Posted by baldbones

I guess I’m asking stiffest..

I suppose I thought that as Max were pretty big and are often cited as stiff(and from my own experience too stiff for me) that bigger was stiffer.

Thanks

OK....

Max oval stays are fairly stiff. C-stay stiffness is first and foremost dictated by the diameter of the tube in the direction of the load, then wall thickness and then of course the overall length.

The caveat I put in there - dictated by the diameter of the tube in the direction of the load - is the big one that most don't know or dismiss out of convenience. The load on the c-stays is primarily sideways bending and then the secondary load of a torsion or twisting load. The larger the stay is in the sideways direction (lateral diameter) the stiffer it will be to resist that sideways movement.

If you think of a Max c-stay they are tall and narrow meaning that they are very stiff up and down (not fully relevant to us here) and less stiff sideways due to the smaller lateral diameter. Some tend to look at the size of it and suppose it must be wicked stiff but they just aren't compared to other designs.

The lateral stiffness of the large and tall oval c-stay is about the same as a round c-stay that has the same diameter as the smaller lateral diameter. Meaning if an oval c-stay is say 17 mm wide it will be roughly as laterally stiff (the direction we care about) as a round c-stay that is 17 mm in diameter. The oval stay will of course be much stiffer in the up/down direction but that is unimportant to us and many would argue it's actually a bad thing.

So....what are the stiffest steel c-stays? They will be the ones with the largest lateral diameter (or width if you will) and then the heaviest wall thickness. Typically speaking oval stays are made that way to give tire clearance and they accept that doing so will make them not as stiff. Practically speaking a thicker wall traditional 7/8" (22.2mm) round chainstay will be effectively stiffer than most any oval stay in lateral bending. The side benefit of the round stay is that it's lighter than the larger oval stay. So I would look for a heavy wall round c-stay if you want a lugged frame with a stiff rear end.

At the risk of this being too self serving.....I have my own round chainstays made that are triple butted with a heavy wall right at the BB shell and then getting thinner as you move to the smaller end. I also have the small end of the c-stay made bigger (15.5 mm compared to the typical 12-13mm end on stock tubes) and this makes for a light and very stiff stay and a bike very responsive to large power inputs. It was a royal PITA to have them made but they have been built into my bikes for a good decade now and they work and feel just right to me.

I hope that is helpful.

dave

[baldbones]

Dave
As ever, a very clear concise explanation.

I was familiar with your preference for round chain stays and your proprietary stays so can I ask how do you counter the inability for round stays to accommodate wider tyres. If you make them longer won’t that counter act the advantage you talked about?

Thanks

Rick

[David Kirk]

Originally Posted by baldbones

Dave
As ever, a very clear concise explanation.

I was familiar with your preference for round chain stays and your proprietary stays so can I ask how do you counter the inability for round stays to accommodate wider tyres. If you make them longer won’t that counter act the advantage you talked about?

Thanks

Rick

Like anything I guess the answer is "it depends."

My straight up road bikes typically have c-stays in the 412-415mm range and at this length a 28 mm tire fits without any special accommodation at all.

If the design calls for stays that are shorter I'll place a very shallow (1 mm) clearance dent to allow the tire to clear without issue.

If the road bike design calls for the tire to be wider than 28 mm then the c-stays will either need to get longer or have a slightly deeper dent. I prefer to make them a few mm longer as that has less effect on stiffness than does making a really deep dent. When I see big stays with a super deep dent to give tire clearance it makes me sad....you may as well put a barn door hinge in there because you are now carrying around all the weight of these big stays without the benefit of the stiffness they may have given. Making the c-stays a bit longer is a MUCH better way to go to get the room compared to deep hinge dents if you want to maintain stiffness and keep the weight low.

How wide a tire do you wish to run?

dave

[baldbones]

Dave
Sorry for the delay in replying but I'm in the UK

Thanks I've always wondered about dent depths and how the affect the ride quality as it seems counterintuitive to dent something!

Ideally I'd like room for a 32mm or a 28mm with fender/mudguard

Thanks

Rick

[David Kirk]

Originally Posted by baldbones

Dave
Sorry for the delay in replying but I'm in the UK

Thanks I've always wondered about dent depths and how the affect the ride quality as it seems counterintuitive to dent something!

Ideally I'd like room for a 32mm or a 28mm with fender/mudguard

Thanks

Rick

Cool - if the right BB shell and dropouts are used you should be able to clear a 32 with very minimal denting of a round stay....no problem.

dave

[baldbones]

Dave
Thank you so much for sharing your knowledge
Really great stuff
Rick

[mhespenheide]

Originally Posted by David Kirk

...
If the road bike design calls for the tire to be wider than 28 mm then the c-stays will either need to get longer or have a slightly deeper dent. I prefer to make them a few mm longer as that has less effect on stiffness than does making a really deep dent. When I see big stays with a super deep dent to give tire clearance it makes me sad....you may as well put a barn door hinge in there because you are now carrying around all the weight of these big stays without the benefit of the stiffness they may have given.
...
dave

First, thank you for your continual input.

Second, although I get that FEA on a single chainstay would show that there's a lot more flex in a dimpled/dented chainstay. Do you think that's still the case for a pair of structural members acting in a trapezoid? Somehow, my very-basic-engineering mind thinks that that might mitigate a lot of the flex. But then, the rear axle might well not be rigid enough or connected well enough to count as a true structural member.
?

(Good to know about 32's. I feel like 30-32mm is the sweet spot for our local poorly-paved bad-repair roads.)

[David Kirk]

Originally Posted by mhespenheide

First, thank you for your continual input.

Second, although I get that FEA on a single chainstay would show that there's a lot more flex in a dimpled/dented chainstay. Do you think that's still the case for a pair of structural members acting in a trapezoid? Somehow, my very-basic-engineering mind thinks that that might mitigate a lot of the flex. But then, the rear axle might well not be rigid enough or connected well enough to count as a true structural member.
?

(Good to know about 32's. I feel like 30-32mm is the sweet spot for our local poorly-paved bad-repair roads.)

All my testing on this has been real world load/deflection tests. Back when Max was a new thing I built bikes with round c-stays and bikes with oval max stays and tested them with a set load and measured the deflection and it was really obvious in this setting even to the eye let alone when measured precisely.

And yes I think the stiffness of the rear axle is a big part of this as it can't make up the the lack of stiffness in the stays.

dave

[baldbones]

Dave
I'm guessing this is why you developed your triple F dropout

With that in mind what's your take on the modern windowed cut out drops that have expanded the cut out the used to be in the old Campagnolo horizontal dropout. Some of the windows seem pretty large to me,

Thanks
Rick

[David Kirk]

Originally Posted by baldbones

Dave
I'm guessing this is why you developed your triple F dropout

With that in mind what's your take on the modern windowed cut out drops that have expanded the cut out the used to be in the old Campagnolo horizontal dropout. Some of the windows seem pretty large to me,

Thanks
Rick

From a pure function standpoint I think the dropout exists simply to allow the rear hub to attach to the c-stay - s-stay juncture....it should close up the end of those two tubes, fix them to each other, and at the same time give a place for the rear axle to attach.

Any material that does not contribute to those two tasks is superfluous adding weight, flexibility, weakness and tough spots to keep clean. I know that it's popular to make dropouts very large and to machine your logo into them and that when well done they can be pretty. I personally have a hard time appreciating the beauty because to my eye the extra material used to get this done is contrived and simply extra.

My dropout is a direct result of this philosophy.....it's as small, light, stiff and strong as can be with no extra material used. It also happens to be shaped so that it's easy to clean with no nooks and crannies to hold chain goop and dirt.

I like simplicity. It's easy to make complicated stuff while making stuff simple is hard but worth the time and effort.

dave

[mhespenheide]

Originally Posted by David Kirk

All my testing on this has been real world load/deflection tests. Back when Max was a new thing I built bikes with round c-stays and bikes with oval max stays and tested them with a set load and measured the deflection and it was really obvious in this setting even to the eye let alone when measured precisely.

And yes I think the stiffness of the rear axle is a big part of this as it can't make up the the lack of stiffness in the stays.

dave

Got it, thank you.