I have a Halfords Carrera Vengeance 2011/12 bike:

Carrera Vengeance Mountain Bike 2011/2012 The Carrera Vengeance Mountain Bike will have you powering up steep hills and across rugged trails in no time. It has a Suntour XCM-V3 suspension fork which soaks up bumps like a sponge, and its SRAM 24-speed gears will make the afore-mentioned hills a piece of cake.

Approximate Weight (KG): 14.6kg

Forks: Suntour XCM-V3

Frame Material: Alloy

Front Brake: Tektro IO Mechanical disc brake

Number of Gears: 24

Rear Brake: Tektro IO Mechanical disc brake

Wheel Size: 26"

Cassette: 11-32T

Chainset: SRAM S200 3.0 chainset

Fork Lock-out: No

Fork travel: 100mm

Frame Colour: Satin Gunmetal

Front Mech: Shimano FD-M190

Gear Shifters: SRAM X4 trigger shifters

Gender: Mens

Handle Bars: Alloy oversize riser bars (30mm rise) (31.8mm diameter)

Headset: Semi integrated

Hubs: Alloy with Q/R

Pedals: Wellgo alloy platform

Quick Release Front Wheel: Yes

Quick Release Rear Wheel: Yes

Rear Mech: SRAM X4 rear mech

Rims: Double wall alloy rims

Saddle: Carrera

Seatpost: 350mm Alloy 31.6

Stem: Ahead aluminium stem

Suspension: Front

Tyres: Kenda Tyres

But the gears are quite bad IMHO. It takes a lot of force to switch gears. I'd also prefer bigger cranks as I pedal on roads a lot. I'm perfectly happy with the brakes and the fork.

I'm looking to buying a set online, e.g. from https://www.merlincycles.com/groupsets-81168/ , but they come in a million sizes. How do I find one that will fit my bike?

1 Answer 1


ANSWER This is a bad idea.

Your bike has 24 gears total, so its probably a 3x8. Thats three front chainrings and 8 cogs on the rear.

You could get more road speed by having a smaller small on the back, or a larger large on the front. However the default rear cassette is 11-32 and 11 is as small as they go. Your specs don't say what the front chainrings are, but on a triple MTB they're likely 26/36/46 tooth, or similar. If you put a 50 tooth front chainring on, then the FD has to be able to get there. Most simply can't handle more teeth.

If I were you I'd look at the gear cables and see that they're moving okay through the outers. The inner wires should be shiny and slide easily. A new set of inner/outers will cost you a lot less than a group and should help sort your shifting. Also measure your chain for wear (ie stretch) and if its over 1% elongated, replace it and the rear cassette if it is worn or starts skipping.

You ride on the road a lot, perhaps you could consider a dedicated road bike? If you've got the budget to buy a new groupset, you're within spitting distance of a complete road bike anyway. And then your N is 2.

Summary: You're on a hiding to nothing doing expensive part upgrades on almost any bike.

  • 1
    Thank you very much Criggie. The thing is I like this bike and can afford to pay 2-300 pounds for an upgrade. Commented May 12, 2016 at 6:45
  • 1
    Agreed that the cables are probably the cause of heavy shifting. According to a reference I found to those cranks they are 22-32-42 so top gear of 42/11 which is 99 inches on 26x2.0 tyres. That's a reasonable top gear for road use, given the tyre size and upright nature of the bike. Classic advice would be learn to pedal smoother/faster, but failing that there are 26-36-48 cranks that should be a straight swap, but would require a longer chain.
    – bertie
    Commented Aug 7, 2023 at 17:53

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.