another dull compatibility question!!

robsy said:

I know this has been discussed many times before but the info i have gathered is confusing and contradictory.
I have a 7 speed drivechain and need new cranks. Will a 9 speed cranset work well enough with my 7 speec chain and fit my current BB? The bike is a 16 yr old Dawes with 400 EX components.

You can use almost any NEW crankset which your wallet will allow ...

However, because your current Bottom Bracket probably has a square taper spindle you will need to buy a NEW bottom bracket, too.

Which crankset(s) were you considering?

Have you considered simply changing the chainrings and/or replacing the bike's current Bottom Bracket?

not exactly sure at the moment. perhaps shimano tiagra but to be honest it doesn't really matter. My pedal dropped out the other day as the threading on one of the cranks is gone.
I have been told before that 9 and 10 speed cranksets would be a problem with my 7 speed setup.

robsy said:

not exactly sure at the moment. perhaps shimano tiagra but to be honest it doesn't really matter. My pedal dropped out the other day as the threading on one of the cranks is gone.
I have been told before that 9 and 10 speed cranksets would be a problem with my 7 speed setup.

I use a 8s chain on a 10s chainrings crank(friction shifters and old C-Record front derailleur from 1986 or so) and it works just fine.

So BB these days arent squared tappered?

robsy said:

not exactly sure at the moment. perhaps shimano tiagra but to be honest it doesn't really matter. My pedal dropped out the other day as the threading on one of the cranks is gone.
I have been told before that 9 and 10 speed cranksets would be a problem with my 7 speed setup.

IMO, your source is generally incorrect ...

The known (to me) exception MIGHT BE, but probably not, a 10-/11-speed Campagnolo crankset because instead of increasing the ramping on the chainrings, Campagnolo chose to machine the large chainring by a fraction of a millimeter to allow it to sit a little closer to the inner chainring ...

And, because Peter indicates that he doesn't have a problem using 10-speed chainrings with an 8-speed chain, you shouldn't either.

robsy said:

So BB these days arent squared tappered?

Welcome to the 21st Century.

alfeng said:

IMO, your source is generally incorrect ...

The known (to me) exception MIGHT BE, but probably not, a 10-/11-speed Campagnolo crankset because instead of increasing the ramping on the chainrings, Campagnolo chose to machine the large chainring by a fraction of a millimeter to allow it to sit a little closer to the inner chainring ...

And, because Peter indicates that he doesn't have a problem using 10-speed chainrings with an 8-speed chain, you shouldn't either.

ah, but i have a 7 speed chain!

robsy said:

ah, but i have a 7 speed chain!

There is generally NO DIFFERENCE between a 7-speed & an 8-speed chain ...

BUT, if there is, then buy an 8-speed chain ... chains have to be replaced at periodic intervals AND your's is probably ready to be replaced.

alfeng said:

There is generally NO DIFFERENCE between a 7-speed & an 8-speed chain ...

BUT, if there is, then buy an 8-speed chain ... chains have to be replaced at periodic intervals AND your's is probably ready to be replaced.

ok, i am more convinced now although a syou say i may have to buy a new BB also if i cannot find a square tappered crankset?

If i were to buy a new wheelset with an 8 or 9 speed hub is it easy enough to use spacers with my old 7 speed cassette?

thanks again

robsy said:

ok, i am more convinced now although a syou say i may have to buy a new BB also if i cannot find a square tappered crankset?

If i were to buy a new wheelset with an 8 or 9 speed hub is it easy enough to use spacers with my old 7 speed cassette?

Yes, a spacer is used when intalling a 7-speed cassette on a wheel with an 8-/9-speed freehub.

BTW. Repacking the bearings on your current wheels is something you should probably consider before buying a new set of wheels.

robsy said:

ah, but i have a 7 speed chain!

7s chain and '8s' chain unless it's really old, are the same dimension but even so, no problem.

its never ending...
will an Octalink BB fit my frame i wonder.

robsy said:

will an Octalink BB fit my frame i wonder.

Yes.

thanks for the help alf

the reason i may get new wheels is because i would like some lighter more responsive ones. but to be honest i don't know whether it is more the frame which gives you a more responsive ride or the wheels.

alfeng said:

Yes.

robsy said:

thanks for the help alf

the reason i may get new wheels is because i would like some lighter more responsive ones. but to be honest i don't know whether it is more the frame which gives you a more responsive ride or the wheels.

It's the rider that gives the bike a responsive ride. Lighter wheels don't provide a significant performance benefit.

As for square taper BB's, Phil Wood still sells them, and the PW square tapers are some of the best you can get.

Maybe consider finding the bottom bracket size of what you have in the frame, find a square taper crank that uses that size, -OR- your bottom bracket is due for replacement anyway, buy a FSA Gossamer crank and bottom bracket on eBay, I saw one this week new for $60-, get the bike shop to install it. -OR- really cheap alternative, have your crankarm fixed with a threaded insert, 20 years ago this worked fine for my loaded touring bike over all the mountains I could find! the bonding agents today are probably even better! I would probably not recommend this fix for a racing bike that I sprint out of the saddle constantly (piece of mind).