8 Speed Shimano Refurb

[EasyPeez]

Hi,

I'm asking this for a friend - he has a Trek Cyclocross bike that is badly in need of new chain and cassette, possibly chain ring too.

It's an 8 speed with triple chain ring Tiagra groupset.

I can't seem to find old Tiagra 8 speed kit online, so would he be best off getting something like one of these?

https://tinyurl.com/y76h5u8q

https://tinyurl.com/yc7ymm3x

Is there much difference in the two, other than the ratios?

And in terms of a new chainset if that's required, would a Deore or Sora 8 speed be the thing to be looking for?

Finally, when it comes to replacing his rear wheel further down the line, will he need to find an 8 speed freehub, or can you just buy a modern 11 speed freehub and add 3 spacers? I wasn't sure if his dropouts would be wide enough to take a modern freehub.

As you can tell, I have no idea what I'm on about as I only have experience of SS and 10 speed!

Cheers.

 

[TheDoctor]

Pretty much any chainset will run 8 speed with no problems, and any 8/9/10 speed hub will take an 8 speed cassette, without a spacer being needed.
I've run a 9/10 speed chainset with 7 speeds before, and 8/9/10 speed Shimano / SRAM cassettes are interchangeable.

 

[EasyPeez]

Thanks for the reply. Good to know that the model of chainset is not critical.

any 8/9/10 speed hub will take an 8 speed cassette, without a spacer being needed

How does that work though? Surely a 10 speed cassette is wider than an 8 speed cassette, and therefore an 8 speed cassette on a 10 speed freehub would need spacers? Not that spacers are any issue, just checking out that I understand the logistics. I have a 10 speed set-up and need a spacer behind my cassette with it being on an 11 speed freehub, so wouldn't the same principle apply when running an 8 speed cassette on a 10 speed hub?

 

[TheDoctor]

No, 8/9/10 speed cassettes are all the same width. The sprockets are thinner and closer together.
When Shimano went to 11 speed they ran out of room and made the cassette a bit wider, hence you needing the spacer to fit a 10 speed cassette on your 11 speed hub. You'd use the same spacer for an 8 or 9 speed cassette though, were you to fit that to your 11 speed hub.

 

[EasyPeez]

Nice one. Thanks for your help :-)

 

[Ajax Bay]

a Trek Cyclocross bike that is badly in need of new chain and cassette, possibly chain ring too.
- 8 speed with triple chain ring Tiagra groupset.
I can't seem to find old Tiagra 8 speed kit online, so would he be best off getting something like one of these?
And in terms of a new chainset if that's required, would a Deore or Sora 8 speed be the thing to be looking for?

Second cassette suggestion looks good.
KMC Z8S 8 Speed Chain
Regarding a new chainring, I'd fit the cassette and chain and see how it goes. Normally it's the middle (of a triple) chainring that needs replacement first (and easy to do). Not likely that a (whole) new chainset is needed but if so, a 9 speed one would be fine as well - plenty of choice as I expect it's a square taper BB.

 

[Kernowdreamer]

As previously stated the Mountain bike and Road 8 speed index systems are interchangable but do be aware that the Deore and Sora cranksets have different chainring tooth count as standard. While this may be a worthwhile change, in some scenarios it can cause compatibility issues with front gear mechanisms as the curvature and shifting ramps on some mechs do not tolerate some non-standard set-ups.
If you do just need to replace a single chainring on the crank then there are several make/model options available to you. The Tiagra triple uses a 5 bolt fixing with the bolts 110mm from the crank axle centre line (110 PCD) on the outer two rings. A search online with the tooth count (probably 50 or 39 tooth) and the PCD should get you there.

 

[Ajax Bay]

The Tiagra triple uses a 5 bolt fixing with the bolts 110mm from the crank axle centre line (110 PCD) on the outer two rings. A search online with the tooth count (probably 50 or 39 tooth) and the PCD should get you there.

I think that you are being to prescriptive here: not all Tiagra triple have a BCD (NB BCD not PCD) of 110mm. Many have 130mm BCD so the OP needs to check which theirs is.
https://www.sheldonbrown.com/cribsheet-bcd.html

 

[EasyPeez]

Thanks for the info.

I was actually wrong about it being a Tiagra groupset; on closer inspection it's just the rear derailleur that's Tiagra. The full spec is this -

http://archive.trekbikes.com/gb/en/2007/trek/pilot10#/uk/en/2007/trek/pilot10/details

 

[Ajax Bay]

It's an 8 speed with triple chain ring Tiagra groupset.
I can't seem to find old Tiagra 8 speed kit online

I expect it's a square taper BB.

wrong about it being a Tiagra groupset; on closer inspection it's just the rear derailleur that's Tiagra

Tiagra 8 speed is 'old' which is why I thought it'd very likely be square taper. The Bontrager Sport chainset (rebadged Truativ) may not be square taper (?ISIS). Whatever, replacement of that is premature. If the middle chainring needs replacing - and you'll be able to tell this once you've replaced chain and cassette and put some 'powahh' on in the middle ring - then 42t BCD 130mm are in short supply so you'll probably need to substitute the 42t with a 39t.
I am in exactly this situation and am currently running a (relatively) new/lightly used 42t inner (from a double chainring, ie without the ramps and pins) as the middle chainring replacement. Jury's still out as to whether it's 'OK'. I have a 39t triple middle ring ready to substitute (couldn't find a middle 42t ring) if I decide it's not good enough.
The Shimano triple FD cages are (apparently) set up / optimised for a 10 tooth difference between large and middle chainrings (eg 42-52), so the 52/39 climb up may not be as good.