[darex]

Hi, I bought used DH bike some time ago with Profile Racing Cranks. I found that they have a little play so I wanted to tightened up a bolts that are in the cranks. The problem is that none of my allen keys fit the bolts socket. The socket is in a good shape. A 5 mm key is too small and a 6 mm is too big. I easily removed these bolts because they haven't been tightened up. Maybe someone have any idea how to tighten up these bolts?

 

[jonKranked]

they are a standard size. I think its a 7/32"

 

[darex]

Ok, Thanks. Funny, because all bolts in my bike are metric.

 

[Wumpus]

they are a standard size. I think its a 7/32"

Yep...One thing you might find is that if you crank them down too much is that they will start to bind the bearings. At least, they do on my bike.

 

[jonKranked]

Ok, Thanks. Funny, because all bolts in my bike are metric.

Yea, I have no idea why Profile does that. Maybe because its a standard bolt you can get at any machine hardware store (NOT home depot).

 

[darex]

Yea, I have no idea why Profile does that. Maybe because its a standard bolt you can get at any machine hardware store (NOT home depot).

The bad thing is that these bolts are BMX specific because they are fine motion screws. They cost almost 16$ at profile racing site .

 

[jamesdc]

All profile stuff i sae because they are an american company and when you tighten the cranks it should not bind the bearings, that means you dont have a long enough spacer inside the bottom bracket.

 

[jonKranked]

All profile stuff i sae because they are an american company and when you tighten the cranks it should not bind the bearings, that means you dont have a long enough spacer inside the bottom bracket.

There's a lot of riders who forego installing that spacer to save a few grams. You just have to pay more attention when you're tightening your cranks.

 

[Wumpus]

All profile stuff i sae because they are an american company and when you tighten the cranks it should not bind the bearings, that means you dont have a long enough spacer inside the bottom bracket.

I have the 'right' spacer. Even had to add a washer to make it bearable.

 

[jonKranked]

The bad thing is that these bolts are BMX specific because they are fine motion screws. They cost almost 16$ at profile racing site .

I used a set of Profile cranks for DH once, and I didn't need to get the DH specific bolts. :biggrin:

 

[darex]

I used a set of Profile cranks for DH once, and I didn't need to get the DH specific bolts. :biggrin:

Maybe you had Profile Racing MTB DOWNHILL but mine are Profile Racing BMX RACE (with e.13 spider) so I think they are not designed for downhill. I use them to save some weight

 

[davep]

The bad thing is that these bolts are BMX specific because they are fine motion screws. They cost almost 16$ at profile racing site .

What are you talking about? How is a bolt 'BMX specific'.....do they wear tight jeans and a chain wallet??? Emo??? Swelbow?

What is a fine motion screw? Has good fine motor control???? '70s way of saying its movement is attractive??

made up words?

You do realize that there is zero difference between the BMX and MTB cranks...???

That is stock off the shelf SAE fine thread flat head socket cap screw....with a countersunk washer....nothing more.

 

[jonKranked]

Maybe you had Profile Racing MTB DOWNHILL but mine are Profile Racing BMX RACE (with e.13 spider) so I think they are not designed for downhill. I use them to save some weight

bmx cranks are plenty strong for downhill, and vise versa. As far as I'm aware it just boils down to a marketing plan, maybe a slight difference in the crank arms themselves, but in terms of the interfacing (spindle, pedals, bolts for spider/sprocket) they're the same. And the MTB cranks come with a spider to use standard mtb chainrings.

 

[w00dy]

It's all the same arms and spindle. They just sell it with different BB cups and (sometimes) a longer spindle. Go to a hardware store. I picked up a box of 25 of those bolts for $16.

The reason it's imperial size is because the cranks were originally designed and made in the US in the early 80's (give of take half a decade, I'm not positive). The interface and hardware never changed. I believe the spindle interface is the same as a 7/8" drive shaft off some sort of race vehicle.

Metric sizing is still in minority use in most US machine shops that I've seen. I can't wait for that to change.

 

[blackspire]

The bad thing is that these bolts are BMX specific because they are fine motion screws. They cost almost 16$ at profile racing site .

I don't know where you live, but you should be able to find those bolts at a well sorted hardware store or any store that specializes in bolts. Buying them for 16$ is way overpriced, you should be able to buy them for 1 $ each or something. Just bring the bolt to the store and say you want one just like it.

 

[-dustin]

I have the 'right' spacer. Even had to add a washer to make it bearable.

might need to add another...

i had to go through the arduous process of installing Profiles not long ago. It was always so easy on my bikes. This one, though, that I got stuck doing for free, took almost 2.5hrs.