Advice on bike gearing

[philb]

Glad you got sorted John. That's interesting about the larger bearing on the 14T freewheel. It has room use more balls or larger balls, it'll probably last forever.

on our commuter bike, I think its 8 speed, the drivetrain still looks absolutely mint.

Just a note on your knee, you might not like a 90rpm cadence but it will not harm your knee like too low a cadence.. you should ensure you've the saddle height fairly bang on ( even 5mm too low could make a difference) and some stiff shoes.
my knees play up from time to time and using higher cadence with less torque is what helps.

[deltona]

Thanks T17. It does look worse in real life than the photo. Night and day between it and the replacement.
'Knocked-off' is probably an apt description.

[Type17]

The variation in the height and shape of the teeth (and the stamped-in 'gates' and 'lift-pins') on the two bigger rings is intentional - it's knocked-off (badly) from Shimano's (and others') designs. Not saying Pro-wheel is a good brand, just that some of the teeth are meant to be shorter and there are stamped-in shapes, to assist chain-lift when shifting.

Here's an upmarket pair of Shimano chainrings for comparison:

[deltona]

Below is a pic of the Prowheel chainrings, so as people can see for themselves.
I'm not saying this is typical, but we bought 2 identical bikes with Prowheel chainrings fitted, and they're both the same.
I just said I'd mention it in case anybody was ordering online and came across the brand.
You can clearly see the huge variation in tooth shape and depth.

[Allspace]

That's great you got sorted and interesting to know about the Tourney parts.
No experience of Prowheel unfortunately but if you are not straining them maybe give it a while before changing them.

[Desmo]

Not to say that they mightn't make ok parts, but I've never heard of them before this thread.

[deltona]

Quick update to close this out, and say thank you to all for the help.

I popped to a local bike store who supply Shimano components (amongst others) and they informed me that with this Tourney freewheel setup it wasn't possible to get anything below 14T due to the size of the internal bearing. Which tied in with what I saw on Shimano's own website. They don't do a Tourney freewheel gearset with less than 14T.

So instead I changed the front chainring. Removed the Prowheel 42-34-24 and replaced it with a Shimano 48-38-28.
The 38T centre ring is where I spend all my time hacking around the city and in traffic, never needing to move to the 48T in variable speed stop/start city traffic.
The 48T has given me what I wanted on a more open straight spin away from traffic - a much more comfortable cadence at a nice cruising speed. (Blew out my knee when a teen, and whilst it gave me jip on and off through the years it's been a persistent and painful weak link over the last 3 years, hence the need for a comfy cadence).

​​​​​​​On a related note - have many on here knowledge of Prowheel components? I wasn't impressed by the quality of the chainrings when I went to count them, and now that it's off the bike it's even more apparent how suspect the quality is. What's the perceived reputation like on their components?

[Allspace]

Looks like you could (if available) go 11- 28 on a new cassette. Rule of thumb you'll need a long cage derailleur for 11-32+. Medium or long cage derailleur as is should be OK. *

*take all this as potential nonsense amd is not applicable at all..

[deltona]

😆 There ain't no fear whatsoever of that!

[bloke]

Come back to us on the result. If you're still spinning out the 11 sprocket in your slacks and shoes, it might be time to approach a local racing club...

[deltona]

Cheers Desmo. I'll have a play with some of those online gear calculators and see what components I can source locally/online.

Thanks to all for the advice and education!

[Desmo]

I'd probably start with a different cassette, something with an 11t. A 42*11 is a lot bigger a gear than a 44*14. At 80rpm one is 38.5kph the other 31.5kph.

I think there's an old rule of thumb that for every 1t you change on the back you'd need to change by 3t on the front, so 42*13 would be a similar gear inch to 45*14.

[deltona]

Thanks Desmo.

The MF-TZ500-7 is listed as a freewheel fit;
https://bike.shimano.com/en-EU/produ...F-TZ500-7.html

What do you guys think would be the best place to start - a 48T front ring, or changing the rear cassette?
I'm not ruling out doing both, but if one option gets me close enough I'll be happy. But which would have the biggest change from the current setup? I reckon I'm about 20% down on a previous comfortable cruising speed at the same cadence.

[Desmo]

Hard to advise with any real certainty without having a bike like that in front of you to check it out. Your max gear for high speed is 42x14 - that's very small. A lot of racers would have a 53x11 or 12. You could increase the size of the biggest ring on the front or you could fit a different cassette on the back. Impossible to know without taking the cassette off whether the rear wheel has a freehub or freewheel fit so couldn't recommend something to purchase online. https://www.bike-discount.de/en/bike...cket/7-speed/? Something with an 11t would make a good difference.

[deltona]

Correct me if I'm wrong, but is it a 42T chainring rather than a 40? I'd suggest swapping out the whole crankset for the other Tourney option which had a 48t as the largest front ring?

Sorry, I'd miscounted. You're correct - it is 42T.

Are cranksets / chainrings mostly interchangeable, or is there anything I need to watch for?

The spindles are marked Prowheel, although I can't see anything on the chainring itself. Should I be looking at sticking to Prowheel, or will a Tourney option fit straight on too?

​​​​​​​Thanks for the advice so far fellas - much appreciated.