Crankset - another question (well two)

martint235

Dog on a bike
Location
Welling
I'm going to have my new crankset fitted tomorrow and have two further questions:

1. I understand the number of teeth etc and am getting a 53/39 set up (shame they don't do 63/39 that'd go quick!!!), but what is the mm measurement? 170mm etc is this the length of the crank arm? If this is the case I'm guessing that longer gives more leverage but shorter would actually be a stronger component (less flex) is this correct?

2. I was set on getting Shimano 105 as everything else that's been replaced lately on the bike has been this group. However I've just noticed Shimano Ultegra (6600 and SL) at around the same price, is there a huge difference in quality?

Ta
 

Chrisz

Über Member
Location
Sittingbourne
1. = mm is the length of the crank arm. There's some debate as to if it makes any noticable difference (172.5mm is standard, 170mm is short & 175mm is long). Usually you want long ones for long legs, short ones for short etc.

2. = I'd go for the Ultegra personally. I don't know if there is any major difference in quality but...............................
 
OP
martint235

martint235

Dog on a bike
Location
Welling
Thanks. In the end the 105s aren't due in until 21st July so I've gone for an Ultegra SL 172.5mm.

Also moving up from a 50/34 to a 53/39 so I should hopefully be a little bit quicker!! :smile:
 

ianrauk

Tattooed Beat Messiah
Yes.. Mart.. of course.. you need to be quicker. Riiigghhhhhttt!! :biggrin::biggrin::laugh:

martint235 said:
Thanks. In the end the 105s aren't due in until 21st July so I've gone for an Ultegra SL 172.5mm.

Also moving up from a 50/34 to a 53/39 so I should hopefully be a little bit quicker!! :smile:
 

Dan B

Disengaged member
I wouldn't worry so much about cranks flexing: the usual reason for shorter cranks (other than shorter legs) is to improve the ground clearance when cornering (or off-roading). This is probably not a concern if you're on a regular bike with a freewheel because you can always coast around corners with the inside leg in the "up" position.
 
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martint235

martint235

Dog on a bike
Location
Welling
It's costing me though!!! Have to buy crankset, ok expected that, BB cups, didn't expect that and a new chain!!! (£28 for a chain!!!! :sad::o). Still I won't have the Sunday lot having a go at me about my chain needing a clean for at least a couple of months!! xx(
 

zimzum42

Legendary Member
With your height, which seemed to me to be about 8'9", I am sure you will want 175mm, but it depend how it feels to you

And you may be quicker on the flat with all that gearing, but the fixie riders will have you on any London hills! :sad:
 
OP
martint235

martint235

Dog on a bike
Location
Welling
zimzum42 said:
With your height, which seemed to me to be about 8'9", I am sure you will want 175mm, but it depend how it feels to you

And you may be quicker on the flat with all that gearing, but the fixie riders will have you on any London hills! :sad:
I've yet to see a fixie rider even attempt Shooters Hill which is on my commutexx(
 
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martint235

martint235

Dog on a bike
Location
Welling
ianrauk said:
You should be able to find a 105 chain for about £17 Mart, BB cups are pretty cheap too

edit: Chain Reaction have 105 chains at £17.99
Apparently it's having an Ultegra chain fitted. I'm hoping to get away without having a new cassette fitted, it's only been on for 3 months!! :sad:
 
OP
martint235

martint235

Dog on a bike
Location
Welling
coruskate said:
I've only ridden my fixie 8 miles so far, but I'm willing to have a go
That's the spirit. I'm sure it can be done but I wouldn't like to try it. At a real push I can make it up on big chainring/big sprocket.

It's worth noting that some people on the Sunday ride (you know who you are) considered it too tough for a Sunday outing though. :sad:
 
OP
martint235

martint235

Dog on a bike
Location
Welling
Ok quick first impressions. Shimano Ultegra SL 53/39 fitted with new chain and new BB. It's not noticably quicker than my old 50/34 however you have to note that one thing that hasn't been changed is my legs!

That said though:

1. Power transfer seems a lot smoother and more responsive. This could be SNTS (Shiny New Toy Syndrome) or just be the change of chain. The old chain was only 3 months old though so i don't believe it had stretched much, it was just knackered.
2. Top speed on the small sprocket is up by about 2mph, need to test this a bit more probably over Biggin Hill at the weekend.

Generally happy with the new set up although I went for the longer crankarms and I just know that at least one time I'll forget to lift my inside foot on a bend. I also know that I will only do this once!:biggrin:
 
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