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I would like to type thank you. 
I not fastest.  I not most agile.  With your help I figured my way to help decrease smog blanket and feel great.  I did ride last winter but 4am hourly rides was cold yet admiration is here to you guys/girls nearer a pole.
Anyway,  budget used so some modify/repair/replace is on hold until later;  much later.

1 issue I have is an old ultegra 8speed wheel set.  A perfectly serviceable unit.  I have tyres to fit and would like to use such with a 23front 28 rear tyre combination on a bike that rolls a 105 9 speed 38 front rear tyre combination.
I understand from reading that the cassette will match the 8 speed rim. 
Is this possible to use both wheelsets with the same cassette and retain derailuar alignment  please?
I feel that that would be the easiest way as a cassette is heaps quicker to change than 2 tyres off,  2 tyres on.
If spacers are required,  are they easily found and cost effective?

8 comments

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Canyon48 [869 posts] 3 months ago
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You should be able to fit any rear wheel in with the same cassette without any adjustment.

Assuming you are using the same manufacturer/speeds on each wheel, shouldn't be an issue.

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kil0ran [812 posts] 3 months ago
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Yes, if the cassette is the same it will work. Not sure if a spacer is needed but if so you might even get one free from a local bike shop, they're included with new wheels and not always required. I regularly swapped wheels with the same model cassette with no issues. At most it might sometimes need a quarter turn on the rear derailleur barrel adjuster. If you're doing a lot of kms (particularly in wet weather) try and use the wheels evenly as you want the chain and cassettes to age equally. An old chain will wear a new cassette faster than a new chain, they need to grow old together to stay a happily married couple  1

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Boatsie [230 posts] 3 months ago
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Thanks. Same cassette. As per wheel swapping I tend to be lazy hence using the same cassette a lot easier to off/on compared to tyres.
Hence chain wear to cassette remaining same combination. I haven't cabled derailuar yet and I haven't fitted one before. Wasn't sure about the alignment issue.
Saves me a heap of work because now old 6speed will be hung as a spare bike instead of stripped and assembled with 9 speed bits.
Reads as easy as 1 fine adjustment screw to centre chain cog rear?
I get data in 4 days to research adjustments.

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kil0ran [812 posts] 3 months ago
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Rear derailleur adjustment appears to be complicated and scary but once you have done it a few times is actually very easy to get it shifting well - particularly on a 8-speed drivetrain where the "good enough" range is larger.

This is a good guide to start with:

https://www.artscyclery.com/learningcenter/shimanorearderailleurs.html

Some further tips:

Before you start you absolutely must have a workstand for this, or some way to have the bike rear wheel off the ground. This is not an adjustment you can do easily/well with the bike upside down.

1. Always set the high limit screw without the cable connected to the derailleur - you can tilt the derailleur back and use the lower jockey wheel to check the correct position (very slightly to the right of the cog when looking from the rear)

2. Before connecting the cable wind the barrel adjuster all the way in (as tight as possible, turn it clockwise) and then loosen it 1 full turn. This gives you more adjustability.

3. When connecting the cable make sure it is in the groove under the clamp nut - the angle is important - check the "Shimano Dealer Manual" for the derailleur

Just pull it hand tight and clamp it, it doesn't need a huge amount of tension at this stage.

The first time you do one it will take you 1-2 hours. Work slowly, pay attention to the guide (particularly which ring you should be in up front). Be very careful when you come to do the Hi limit screw.

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Boatsie [230 posts] 3 months ago
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Thanks.
I guess I'm saving towards a work stand.
Hint 1 scares me aye. Hopefully the wheels sit the cassette at the same position. Can't see me being bothered to loosen cable and retighten each change.
I hope they seat cassette equally, with or without spacers or I think it might be just 1 tyre set until worn. Usually takes me longtime to wear tyres.
Thanks heaps.

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mikeymustard [30 posts] 3 months ago
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Boatsie wrote:

Thanks. I guess I'm saving towards a work stand. Hint 1 scares me aye. Hopefully the wheels sit the cassette at the same position. Can't see me being bothered to loosen cable and retighten each change. I hope they seat cassette equally, with or without spacers or I think it might be just 1 tyre set until worn. Usually takes me longtime to wear tyres. Thanks heaps.

You should only have to do "Hint 1" when you first fit the derailleur. The cassette should sit the same on both wheels; the only way to know if it all works is to try it, but I think a 9 sp cassette should fit an 8 sp freehub without need for spacers. If there's any adjustment needed it should only be a twiddle of the cable adjuster and maybe resetting the hi/lo screws - still quicker than changing tyres!

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Boatsie [230 posts] 3 months ago
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Thanks. Laughing aye. Spent car running costs to set up commuting via bicycles and heavy hub gumtree $130 bargain flys because so comfy that there is no chore. I wouldn't have thought that prior to riding such.
Plan now simple thanks to you guys with the derailleur hints. Assemble, ride, then later on just play with 2nd rim to attempt a no adjustment swap out. Really lazy dude, even minor adjustments I couldn't be bothered with and terrain local has most cycling disciplines covered. If I can't space identical I'll keep spare in case of buckle or similar and ride to suit tread until such occurs.
Hoping they share alignment.

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kil0ran [812 posts] 3 months ago
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Boatsie wrote:

Thanks. Laughing aye. Spent car running costs to set up commuting via bicycles and heavy hub gumtree $130 bargain flys because so comfy that there is no chore. I wouldn't have thought that prior to riding such. Plan now simple thanks to you guys with the derailleur hints. Assemble, ride, then later on just play with 2nd rim to attempt a no adjustment swap out. Really lazy dude, even minor adjustments I couldn't be bothered with and terrain local has most cycling disciplines covered. If I can't space identical I'll keep spare in case of buckle or similar and ride to suit tread until such occurs. Hoping they share alignment.

You should be good - I never had to tweak alignment when I swapped wheels. Worst case is that you'll find a slow shift somewhere in the middle of the cassette and that's very easily tuned by  a quarter turn of the barrel adjuster. Most times it will ride perfectly. If its noisy in one cog simply shift to the next one. Its nearly always the middle cogs because you use them the most and the cable wears in the shifter.

With rear derailleurs the most important thing is to get the limit screws set as dropping a chain off the small cog will scrape the frame, and off the big cog will put it into the spokes and possibly damage the wheel. Limit screws should be a one-time only job as any slow/noisy shifting can be easily tuned with the barrel adjuster.

With all these adjustments make small changes and test. Half turns of a limit screw or barrel adjuster make big changes.