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[u]The "can i use a new 10 speed crank on my 8 speed setup" question.[/u]
I have recently got an old (2007 ish) road bike, hardly ridden. It's a shimano 8 speed. I want to know if i can replace the flexy square taper crank with something new like a Tiagra 4700. Now as far as i understand these newer chainsets, which are marketed as 10/11 speed, are still compatible with older 8/9 speed setups due to them having slightly narrower teeth to accommodate the thinner chain needed for a 10 or 11 speed setup. So the fatter chain of an 8 speed won't have any problems fitting over the narrower teeth of a newer 10/11 speed crank.
Am i right? I'll be keeping my shifters, rear mech, cassette and chain so there shouldn't be a problem, should there?
[u]The gearing ratios question[/u]
At the moment i have a triple chainset with a 30T chainring up front and an 11-30 cassette. So 30T to 30T in the easiest gear. If i buy a compact chainset with a 34T chainring, whats the equivalent rear gear?
Reason i ask is because the bike came to me with an 11-23 cassette but i found myself having to get off and push up some of the hills around here so i swapped the cassette out for an 11-30T which seems perfect. The rear mech is a decent length but still seems to catch on this larger 30 tooth cog, the jockey wheel sort of sits against it and makes a trickling sound but as i'm not in this gear very often i can live with it. But i think if i were to try and push it to an 11-32 cassette i would have problems, so that's not a route i want to go down.
I know nothing about calculating gear ratios i've tried reading about them but it confuses me, i'm hoping someone can come along and just tell me that 30-30 is the equivalent of 34-XX.....
For the first bit I think the answer is yes but don't come looking for a refund if I'm wrong.
The second one is easy. The equivalent to a 30:30 ratio is a 34:34 ratio.
The simplest formula for gear ratios is to divide the front by the back. so both of those are 1
A 34:23 is 1.48 so considerably bigger. You may struggle to get a 34t on the back but a 30 gives you 1.13 which may be manageable.
To solve your mech issues you need to wind the B-screw in all the way
http://www.parktool.com/blog/repair-help/rear-derailleur-adjustment
If that doesn't work and you have a box of bits you might be able to find a longer one. The other option is to take it out and put it in from the other side so the head sits against the hanger - normally gives you an extra mm or so length.
The park tool site is very good with official/proper help on maintenance. When you want a more practical solution to a problem then people often refer to the late (great) Sheldon Brown http://www.sheldonbrown.com/
As above,
1. Yes
2. 34
Note that IME many road mechs will struggle with a 34 and you may well need to use an MTB mech. (The parallelograms are angled slightly differently AFAIK to reflect the different gradient of the cassettes.)
Thanks chaps that's exactly the info I was looking for.
Surely new 11 speed road cassettes go up to 34?? Perhaps the new mechs are just designed to be a little bit longer to accommodate a wider range cassette. The 23T that was on there was useless!
Also would I be able to swap out the 34T for a 30? Or would the jump from 30 to 50 be too much for the front mech to handle?
Surely new 11 speed road cassettes go up to 34??
Don't think so. There are less jumps between sprockets so you maintain cadence. The road marketing seems to assume that anything bigger than a 28 is not needed with a 34 on the front. Fine for some but not for others. Mechs are generally getting shorter to save weight. Only short and medium now or can you still get long?
Also would I be able to swap out the 34T for a 30? Or would the jump from 30 to 50 be too much for the front mech to handle?
I think you'd struggle there is a tech doc somewhere on the shimano website that says what the gap between the biggest and smallest gear can be. You could try wading through that and see what you can find.
So a 34/30 would = 1.133333333333333
My second chainring is 26T and 30/26 = 1.1538
So if I can get up all the hills without using the 30t cog I can use a compact
Surely new 11 speed road cassettes go up to 34?? Perhaps the new mechs are just designed to be a little bit longer to accommodate a wider range cassette.
Some will be, yes. That's the "IME"/"most" caveat 😉
Also would I be able to swap out the 34T for a 30? Or would the jump from 30 to 50 be too much for the front mech to handle?
It's too much for decent shifting, but more importantly if you're looking at a compact road double (110mm BCD) then the smallest you can fit is a 34. For a 30 you'll need a triple (mountain or road) or possibly a new-fangled (compared to anything I have) mountain double.
Out of interest, if you care about the lower gears, why are you replacing a triple with a compact double? Personally I'd take the triple every time, but everyone's different.
Surely new 11 speed road cassettes go up to 34??
Nope. 4700 Tiagra goes to 34 but that is 10 speed.
105/Ultegra go to 32 with a GS rear mech
DA 9000 = 28 max
Are square taper bottom brackets/cranks really flexy?
you could buy a road triple chainset and not use the outer ring (it could be removed or not)
handy website for what works advice
[url= http://www.cyclingabout.com/wider-gear-range-road-shifters-gears-for-easier-hill-climbing/ ]Link[/url]
If you want a double with low road gearing then the Spa TD-2 "super compact" will be what you want.
http://spacycles.co.uk/products.php?plid=m2b0s109p0
Though to be honest I'd just put an outer ring on as well, given that you've presumably already got triple shifters.
Probably not what you want to hear, but there's plenty of anecdotal evidence that a decent square taper BB will outlast an external-type BB
+1Are square taper bottom brackets/cranks really flexy?
The chainrings on a 10s crankset may be closer together (narrower chain) than on an 8s, will that cause problems when going from the smaller ring to larger with a wider chain? Possibly not, but I'd consider it
I have two bikes with identical framesets; one has square taper and one has GXP. On another frameset I've used both square taper and HT2. If there is a difference in flex I don't notice it. They're all absolutely fine, and I'm 14 stone.
Out of interest, if you care about the lower gears, why are you replacing a triple with a compact double? Personally I'd take the triple every time, but everyone's different.
I've just seen a nice new Shimano Hollowtech double on the cheap, no other reason than that really. If the triple was the same price i'd definitely go for that.
Are square taper bottom brackets/cranks really flexy?
I would guess that it depends on the crank and bottom bracket in question. Not all cranks are created equal, are they? That's why a Dura Ace costs more than a 105. My Truvativ square taper cranks from 2007 don't look stiff, they don't feel stiff and even though they came to me on a barely used second hand bike they already have a squeak. (disclaimer, i'm not going to enter into a discussion about where the creak may or may not be coming from).
Surely new 11 speed road cassettes go up to 34??
Nope. 4700 Tiagra goes to 34 but that is 10 speed.
So there are some road cassettes/ derailleurs that allow a 34T cassette then! That was all i was getting at, to know if it was possible. I've not long ago spent money on a 30T cassette anyway so i'm not replacing it.
If you want a double with low road gearing then the Spa TD-2 "super compact" will be what you want
I don't want a double with low road gearing, i just wanted to know if the crank i had seen for sale was compatible with my old setup. Thank you anyway.
I have two bikes with identical framesets; one has square taper and one has GXP. On another frameset I've used both square taper and HT2. If there is a difference in flex I don't notice it. They're all absolutely fine, and I'm 14 stone.
You haven't seen my chainset 😆
And besides all this, i just want a new chainset.
The 23T that was on there was useless!
Really even when using a 30 on the front? That's a pretty low gear for a 'normal' road bike.
Although I'd still change from a triple to a double, as triples suck, but if you were struggling on a 30-23 then you'll probably want a long cage mech and big cassette fitting also.
Wanting a new chain set is fine
Buying one as it happens to be cheap doesn't make sense if it then means your not getting the ratios you want.
large discount doesn't give better value if it is not the product you want
I'd go lower spec triple (The bike I ride most has an Alivio triple. When I press on the pedals the bike moves forward. It also shifts well enough...)
PS I always thought that Dura Ace chain-sets cost more than 105 chain-sets as a sort of Shimano based social equality experiment. Moping up spare cash from higher earners.
Really even when using a 30 on the front? That's a pretty low gear for a 'normal' road bike.
Not when you live in Calderdale.
Although I'd still change from a triple to a double, as triples suck
go on then enlighten me. why is that then.
if you were struggling on a 30-23 then you'll probably want a long cage mech and big cassette fitting also
Well as pointed out above:
30/30 = 1 (what i'm on now.)
30/26 = 1.153 (my second cassette cog with what i'm on now)
34/30 = 1.1333 (what i'd be on with a compact)
So the second cog on the setup i have now should actually be a bit harder than what it will be with a 34t up front.
Buying one as it happens to be cheap doesn't make sense if it then means your not getting the ratios you want.
Really? well in that case i'd better do some research 🙄
large discount doesn't give better value if it is not the product you want
right...
I'd go lower spec triple (The bike I ride most has an Alivio triple. When I press on the pedals the bike moves forward. It also shifts well enough...
gears are boring, this is a fact.
PS I always thought that Dura Ace chain-sets cost more than 105 chain-sets as a sort of Shimano based social equality experiment. Moping up spare cash from higher earners.
I can understand how someone with an Alivio chainset might think that.
I'm beginning to understand why it's called the "dark" side.
I've got a Deore one as well!!!
And a Campag one!
Talk to a touring specialist like Spa Cycles as touring bikes need lower gears - 30x30 is a really low gear for an unladen road bike, More suited for winching you way up 30 degree gravel tracks IME. I would also worry less about the need for bigger chainrings - with steep downhills you'll be freewheeling at speeds beyond pedalling in no time. OP doesn't mention fitness or cycling ability - maybe within a few months of riding fitness and strength will improve to make such questions redundant?
Not sure if it has been mentioned yet but you won't want a double with your triple shifter...
I'd like to defend the OPs desire for low gears
I'm sure I've always been suspicious that the road seen hasn't been that logical on gearing
Since hearing Bertie used 34x32 I've relaxed in the knowledge that if you can sustain over 400W and weigh under 70kg then it's not surprising that an amateur might want a gear lower than that
https://roadcyclinguk.com/gear/alberto-contador-vuelta-a-espana-on-sram-red-wifli-9955.html
The square taper isn't flexy, you can't use your triple shifters with a double chainset and if you could you'll also have to run some right mismatch parts to use a big enough cassette to give you gears anywhere near as low as the triple does now.
Leave as it is or buy a whole new group set.
The square taper isn't flexy, you can't use your triple shifters with a double chainset and if you could you'll also have to run some right mismatch parts to use a big enough cassette to give you gears anywhere near as low as the triple does now.
That is not my memory of how things work