50/34 Chainring to 50/38? Pls help

hockeyjunkie

Hi, I would appreciate an advice here pls
My son has a bike with a Shimano 105 compact cassette, which is 50/34.

Now that he's moving to the next age group with a different rollout limit, I need to replace the 34t chainring with the 38t one (38 gives the right gears combinations).

Could you please advice (and ideally point me to) the right chainring?

Would, for example, the Dura-Ace 9000 38t chainring that Wiggle has here work with this set up? I don't know if Dura-Ace chainrings are compatible with 105s, as this is about where my bike knowledge ends...

Any other suggestions will be appreciated!

amrushton

If it's a bcd (bolt circle diameter) of 110 (which 50/34 is) and a 4 arm spider it will work. Other brands (FSA, middleburn) are available.

arlowood

hockeyjunkie said:

Hi, I would appreciate an advice here pls
My son has a bike with a Shimano 105 compact cassette, which is 50/34.

Now that he's moving to the next age group with a different rollout limit, I need to replace the 34t chainring with the 38t one (38 gives the right gears combinations).

Could you please advice (and ideally point me to) the right chainring?

Would, for example, the Dura-Ace 9000 38t chainring that Wiggle has here work with this set up? I don't know if Dura-Ace chainrings are compatible with 105s, as this is about where my bike knowledge ends...

Any other suggestions will be appreciated!

If you read the reviews in the Wiggle link you posted you will see the guy who posted the last one on page three pf the reviews has done exactly what you are proposing. ie fitting the DA ring to replace a 34T on a compact chainset

imposter2.0

amrushton said:

If it's a bcd (bolt circle diameter) of 110 (which 50/34 is) and a 4 arm spider it will work. Other brands (FSA, middleburn) are available.

^^ this. Any compatible chainring will do the job. Should be able to find cheaper than DA perhaps. Presumably you are locking-off the 50t outer? What are you using on the rear?

IIRC, when my son was U12 he used 42 outer and 15 on the rear. So he kept the 34 inner.

Bit confused though - I remember youposted on the track forum back in December where you said your son was staying in youth C for 2020 - but now you're saying he's moving up?

hockeyjunkie

imposter2.0 said:

amrushton said:

If it's a bcd (bolt circle diameter) of 110 (which 50/34 is) and a 4 arm spider it will work. Other brands (FSA, middleburn) are available.

^^ this. Any compatible chainring will do the job. Should be able to find cheaper than DA perhaps. Presumably you are locking-off the 50t outer? What are you using on the rear?

IIRC, when my son was U12 he used 42 outer and 15 on the rear. So he kept the 34 inner.

Bit confused though - I remember youposted on the track forum back in December where you said your son was staying in youth C for 2020 - but now you're saying he's moving up?

Hi there - well remembered
Matter of fact I have 3 children all riding in different age groups (E/D/C)

For the upcoming road season I'm transferring my oldest boy's bike to another son who's in the U10 group. 34t chainring (with 50t blocked out) works well for the U12 category, as the 34x12 combination is bang on within the limit. For the U10 though 34t isnt great, as the closest ratio of 38x14 is 30cm under the limit, which is a bit too much. Hence the idea is to target the 38x15 combination, changing the chainring for 38t and swapping the cassette for 14x.

Been looking at different chainrings on the internet all day and ultimately got lost hence decided to ask the collective forum wisdom for advice

imposter2.0

3 kids - that's gonna be expensive

Can't remember what my lad ran in U10 - too long ago. He's 2nd yr U16 now.

simon_e

One of the best places to look for chainrings is SJS:
https://www.sjscycles.co.uk/chainrings/

Some info about youth gearing:
https://www.matlockcyclingclub.org.uk/youth-gear-restrictions