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is it possible to swap freehubs?

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is it possible to swap freehubs?

Old 05-15-22, 08:21 AM
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jadmt
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is it possible to swap freehubs?

Is it possible to swap a freehub from an ealy 1990's shimano XT 7 speed hub to a newer 9 speed hub? I have a nice wheel and XT 7 speed that I would like to be able to run a cassette from this group. I have it already set up with a XTR hub but the wheel does not match my front wheel and the wheel is pretty wore out on the braking surface and the hub does not spin as smooth as my XT wheel. this is the group I am running. thanks in advance.https://boxcomponents.com/products/b...shift-groupset
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Old 05-15-22, 09:18 AM
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Well it probably depends on exactly which Deore-XT free hub you have. There were a bunch of them over the many years Deore has been a name. If yours was originally 7 speed, then 8 as you say you currently have isn't unreasonable. However 9 might be a stretch. But again, it depends on the specific model of the hub/free hub. The older, the less likely.

Mid 1990's was 8 speed I think. But was your free hub originally a 7 speed that could also handle a 8 speed or is it a 8 speed that with spacer might have ran a 7 speed and also has the length for a 9 speed. Again, that exact model and version number is important.

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Old 05-15-22, 10:33 AM
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8,9 and some 10 use the same freehub body.
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Old 05-15-22, 10:59 AM
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I've done a number of freehub body swaps from 90's hubs. I'm pretty certain that if you have a 7 speed "XT" freehub, it is most likely an FH-M732. It is a Uniglide UG/ Hyperglide/HG freehub body that will accept both. The 6 speed is an FH-M730 was UG only. If you are going to use an 8 or 9 speed then any "compatible" 8-10 freehub body will work.

Compatibility is pretty easy with Shimano, but there are a few things to understand. In addition to getting the correct spline (stay away from RM-33), an important aspect of the swap is to get one that fits the depth of the hub recess. An FH-M732 has a deep freehub body recess and needs a freehub with a thick flange/shoulder. I've posted this pic a number of times...




The upper left is a freehub body off of an FH-M732, The one below is off of an FH-M650. Both are 7 speed UG/HG and from the same era. Upper right is a 9 speed from an FH-7700.

You have a couple of things to consider forward. I wouldn't bother with a vintage hub unless you can find one that in great shape and reasonable. I know an FH-M737 fits as well as the LX counterparts, but an FH-M760 won't. If you go to a modern 8-10 freehub, I don't know which ones have a thick/deep flange. If you find one that will work, buy a complete freehub and not just the body because Shimano did change the cones slightly and the dust seal diameter over the years.

John

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Old 05-15-22, 11:29 AM
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I just noticed you have an XTR setup. I'm almost certain the FH-M900 and, I know, the FH-M950 freehub body would fit.

That doesn’t fix the XTR freehub cup/cone spinning concerns. But the only way to know if there is damage is to open up the XTR hub and check the bearing surfaces. If the DS is fine, and the flange fits, you just have to re-grease and move everything over. Replace the ball bearings.

John

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Old 05-15-22, 01:06 PM
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this my XT wheel, which I am hoping to keep as it matches my front wheel and is in great shape. I can not exactly make out the numbers on the hub but it is from a 1993 bike and I know would have been new when I bought it in 1993.




Last edited by jadmt; 05-15-22 at 01:31 PM.
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Old 05-15-22, 02:02 PM
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the front hub that was with this group is an XT M730.
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Old 05-15-22, 02:20 PM
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Originally Posted by 70sSanO View Post
I've done a number of freehub body swaps from 90's hubs. I'm pretty certain that if you have a 7 speed "XT" freehub, it is most likely an FH-M732. It is a Uniglide UG/ Hyperglide/HG freehub body that will accept both. The 6 speed is an FH-M730 was UG only. If you are going to use an 8 or 9 speed then any "compatible" 8-10 freehub body will work.

Compatibility is pretty easy with Shimano, but there are a few things to understand. In addition to getting the correct spline (stay away from RM-33), an important aspect of the swap is to get one that fits the depth of the hub recess. An FH-M732 has a deep freehub body recess and needs a freehub with a thick flange/shoulder. I've posted this pic a number of times...




The upper left is a freehub body off of an FH-M732, The one below is off of an FH-M650. Both are 7 speed UG/HG and from the same era. Upper right is a 9 speed from an FH-7700.

You have a couple of things to consider forward. I wouldn't bother with a vintage hub unless you can find one that in great shape and reasonable. I know an FH-M737 fits as well as the LX counterparts, but an FH-M760 won't. If you go to a modern 8-10 freehub, I don't know which ones have a thick/deep flange. If you find one that will work, buy a complete freehub and not just the body because Shimano did change the cones slightly and the dust seal diameter over the years.

John
So I think I have a 732 or possibley 737 as the lettering is hard to read, the front is an M730 and would have been part of the same group set in 1993. . you need to talk to me like you are talking to a 1st grader...When you say you wouldn't bother with a vintage hub do you mean the one I have? I really want to keep it as the wheel is in great shape and matches my front wheel. I am trying to do it on the cheap. I had a bike shop install the Box 4 8speed and they ended up swapping a non matching rear wheel that the tech found at a bike coop for cheap but the wheel does not match and the brake surface is really worn and the XTR while not terrible is not nearly as smooth as my original wheel and has a slight amount of side to siide play in it. when I originally talked to him he said the Box 4 would fit on my XT wheel but when he went to install the box 4 rear cassette he said it did not fit because of the free hub was too short. thanks
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Old 05-15-22, 02:45 PM
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Your rear hub is an FH-M732. Can you post a pic of your XTR hub?

John

Edit Added: Can you measure the dropout width on your bike?

Last edited by 70sSanO; 05-15-22 at 03:13 PM.
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Old 05-15-22, 03:32 PM
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Originally Posted by 70sSanO View Post
Your rear hub is an FH-M732. Can you post a pic of your XTR hub?

John

Edit Added: Can you measure the dropout width on your bike?



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Old 05-15-22, 03:40 PM
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Originally Posted by 70sSanO View Post
Your rear hub is an FH-M732. Can you post a pic of your XTR hub?

John

Edit Added: Can you measure the dropout width on your bike?
standard 135mm
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Old 05-15-22, 04:57 PM
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This is not exactly first grade material, but here goes.

Your 7 speed freehub body is not as wide as an 8 speed freehub body which is why your 8 speed cassette didn't fit; 8 speed cassettes are about 3.5mm wider.

Both OLD (over locknut dimension) width for both hubs is 135mm.

When you install the 8 speed hub, you will need to remove some of the spacer width or your hub will be wider than 135mm.

The way I do it, is to measure from the outside of the lock nut to the edge of the freehub body of the 7 speed hub and then measure the same to the 8 speed hub. Because they are both 135mm OLD, I have found that sometimes the 7 speed has a bit more clearance on the Drive side (DS) to the drop out. As an example, if the 7 speed locknut to front edge of the freehub body is 7.5mm and the 8 speed is 6.5mm, you will pick up 1.0mm from the DS and only need to remove "ABOUT" 2.5mm to 3mm of spacers from the Non-drive side (NDS).

The one kicker that has not been discussed is that when you remove/add spacers, (or freehub body length), that is not equal on both sides of the hub, (DS and NDS), the rim will not be centered between the dropouts. You will have to re-dish the wheel. In this case you will need to move the rim toward the DS.

If you have a truing stand and have trued wheels before, I set the wheel up to do a righty tighty - lefty loosey. Start at the valve hole and the spoke going to the right side (DS) gets turned counter clockwise (tighter) 1/4 to 1/2 of a turn, then the spoke going to the left side (NDS) is turned clockwise (looser) the same 1/4 or 1/2 turn. The reason I do this is because your brain may freeze as you go through the monotony and looking at the direction of the spoke tells you how to turn it.

If it were me, I'd swap your XTR freehub body with the DS cone and DS dust seal and any DS spacers. Drip some Phil's Tenacious oil, or similar, into the freehub body. I usually get an awl or thick needle to create a slight gap between the rear seal and body (a 30 year old plastic seal may not survive removal) and just let it drip through. It may take a while, but you should hear the ratchet pawls quiet down. Put everything together. It will be a great learning experience, can't hurt your XT wheel, and make a future swap with a better freehub body a piece of cake.

Welcome to the 2nd grade.

John

Last edited by 70sSanO; 05-15-22 at 05:12 PM.
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Old 05-15-22, 06:14 PM
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Originally Posted by 70sSanO View Post
This is not exactly first grade material, but here goes.

Your 7 speed freehub body is not as wide as an 8 speed freehub body which is why your 8 speed cassette didn't fit; 8 speed cassettes are about 3.5mm wider.

Both OLD (over locknut dimension) width for both hubs is 135mm.

When you install the 8 speed hub, you will need to remove some of the spacer width or your hub will be wider than 135mm.

The way I do it, is to measure from the outside of the lock nut to the edge of the freehub body of the 7 speed hub and then measure the same to the 8 speed hub. Because they are both 135mm OLD, I have found that sometimes the 7 speed has a bit more clearance on the Drive side (DS) to the drop out. As an example, if the 7 speed locknut to front edge of the freehub body is 7.5mm and the 8 speed is 6.5mm, you will pick up 1.0mm from the DS and only need to remove "ABOUT" 2.5mm to 3mm of spacers from the Non-drive side (NDS).

The one kicker that has not been discussed is that when you remove/add spacers, (or freehub body length), that is not equal on both sides of the hub, (DS and NDS), the rim will not be centered between the dropouts. You will have to re-dish the wheel. In this case you will need to move the rim toward the DS.

If you have a truing stand and have trued wheels before, I set the wheel up to do a righty tighty - lefty loosey. Start at the valve hole and the spoke going to the right side (DS) gets turned counter clockwise (tighter) 1/4 to 1/2 of a turn, then the spoke going to the left side (NDS) is turned clockwise (looser) the same 1/4 or 1/2 turn. The reason I do this is because your brain may freeze as you go through the monotony and looking at the direction of the spoke tells you how to turn it.

If it were me, I'd swap your XTR freehub body with the DS cone and DS dust seal and any DS spacers. Drip some Phil's Tenacious oil, or similar, into the freehub body. I usually get an awl or thick needle to create a slight gap between the rear seal and body (a 30 year old plastic seal may not survive removal) and just let it drip through. It may take a while, but you should hear the ratchet pawls quiet down. Put everything together. It will be a great learning experience, can't hurt your XT wheel, and make a future swap with a better freehub body a piece of cake.

Welcome to the 2nd grade.

John
thank you...i think failed ...sounds like more than I want to do. I think I will look for a used mavic 231 with a hub that will work. thank you for taking the time to help.
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Old 05-15-22, 07:59 PM
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Originally Posted by jadmt View Post
thank you...i think failed ...sounds like more than I want to do. I think I will look for a used mavic 231 with a hub that will work. thank you for taking the time to help.
No problem. Hopefully it is info that someone can use.

John
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Old 05-16-22, 08:26 AM
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Freehub body swaps aren't that difficult, especially on 135mm OLD. If it were 126mm you might have to move spacers and redish the wheel but with 135mm OLD there should be room for the new 8/9 body. Take a look at Sheldon Browns article for some info: https://www.sheldonbrown.com/k7.html#transplant . I did the same on a '96 mountain bike with 135 OLD: no moving spacers or dishing needed.
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Old 05-16-22, 09:03 AM
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Originally Posted by mitchmellow62 View Post
Freehub body swaps aren't that difficult, especially on 135mm OLD. If it were 126mm you might have to move spacers and redish the wheel but with 135mm OLD there should be room for the new 8/9 body. Take a look at Sheldon Browns article for some info: https://www.sheldonbrown.com/k7.html#transplant . I did the same on a '96 mountain bike with 135 OLD: no moving spacers or dishing needed.
Yes, I understand it is possible. By 1996 8 speed was available so I can understand that on some setups the 1st cog to dropout clearance on the DS could be great enough to not need any re-dishing. I honestly don’t remember if I didn’t do any re-dishing on the 135’s I’ve done.

I would think there could be slight chainline issues if the freehub attach point in relation the the crank was the same. Or it could have improved the chainline if the original 7 speed was off.

John
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Old 05-16-22, 09:59 AM
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John is absolutely correct. Being the lazy SOB that I am, my line of sight judgment was that it was good enough. This discussion has spawned an after the fact analysis. I hope my assumptions are correct. Total cassette width of 7 spd IG is 32.4 mm and HG 31.9 mm. Total cassette width of a 9 spd HG is 36.5 mm (all according to Sheldon Brown). That means the center position is at 16.2 mm for 7 spd IG, 15.9 mm for 7 spd HG and 18.25 mm for 9 spd. That means the center cog of the cassette is shifted outward 2.05 to 2.30 mm when moving from 7 spd to 9 spd. HG 9 spd cog spacing is 4.34 mm. So the chainline is altered about 1/2 a cog spacing by not dishing the wheel. As I recall my conversion worked great without dishing but I'm also old and memory may not be the best. I suppose in the end it is somewhat of a value judgment. One could first do the swap without moving spacers and re-dishing and see if it is "good enough". Long ago in the USAF when we did a temporary repair to keep it flying we would end it with the statement " that's good enough for government work". We did always go back and correct it................eventually.
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Old 05-16-22, 10:10 AM
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ADDENDUM: Also note that the recommended front chainline measurement for Shimano MTB triples is 47.5 to 50 mm (47.5 preferred) so there can be some leeway in chainline. I realize I just refernced the measurment at the crank and we are discussing the cassette position.
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Old 05-16-22, 11:18 AM
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Being off by a few mm’s running 7-9 speed is probably not a real concern.

On my mtb’s I’m running 2x on a triple crank with the middle/inner positions.

It works well in that the large chainring, in the middle position, hits all the cogs.

The inner is a bit stretched but since going with a 40t cog, the small-small is not a good selection due to chain slap on rougher terrain.

John
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Old 05-19-22, 11:34 AM
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I'm not sure I could do this swap with an XTR hub, I usually look for cheaper hubs, such as Alivo, to make the new 7sp.

As for the hub wear, I'd look at why this is not spinning as smooth as your rear. It could be something that is fixable, and you'll need to take it apart to get the freehub off anyway. Brake wear and miss match, which you also mentioned, I can understand.

I don't think the XTR M900 has it, but sometimes there are washers between the freehub and hub, make sure you note exactly how this is setup. I've had to take a hub apart a 2nd time and flip the washer before.

Make sure you check / adjust the wheel dish after.
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