Correct frame/wheel size and bike recommendations for a 12yr old

jujitsoup

Looking for some advice as I’m a little out of the loop. I did a bit many years back but haven’t done anything for a long time.

My lad is 12 and 5’ 4” and I want to get him a new MTB for Christmas as he’s currently using his mothers old GT. I want to spend up to £400 but want the bike to have hydraulic disc brakes. I’ve found the Trek Marlin 5 2019 which seems to tick most of the boxes (specs, colours, cred with his mates). The issues I have are getting the correct size frame for him (Christmas surprise for a year of hard work) and also finding a bike with the right sized wheels for him.

I bought a Merlin (Preston) years back and it has 26” wheels and my wife’s GT also has 26” wheels. It now looks like 27.5” or 29” are the standard sizes. Am I reading this right? The Trek has 29" wheels coming with the frame size which we think would fit him, but I'm concerned this wheel size is too big his size (tall-ish, skinny). He mainly rides on the road and sometime goes off road with his mates.

Would appreciate it can anyone give me some advice on the approx the right size frame for him, the right wheel size at this age/size and any other bike recommendations within my budget (can also be a previous years bike).

Thanks.

steve_sordy

A 26er may be cheaper as while many are still made, the market has moved away from them towards 27.5 and 29. But in the same way that small kids have bikes with small wheels and really tall people seem to suit 29ers better, then for those of heights in between, inbetween wheel sizes seem to suit. I'm 6'1" and I've happily ridden 26, 27.5 and 29. My 11 year old grandson is very happy on his 26er as it is light and manoeuvrable. Also, because the fork and wheels are suited for 26ers, they were a lot cheaper when I wanted to buy upgrades! His next bike might turn out to be a 27.5 simply because of fit, price, availability and of course his needs and ability. But if it was a 26er, it wouldn't bother him or me. I would not get him a 29er as small framed bikes just do not look right with 29er wheels (IMO).

When you are on a website looking at a bike of your choice, look around the the page for the "size guide". It is usually labelled as such but it could be a small rectangle with a tape measure inside it. I just googled the Trek Marlin 2019 and ended up on the Evans website and according to the size guide there. Those who are 5'2" to 5'6" are suited to a 14" to 16" frame size with a bike that is usually labelled "Small". Some manufacturers who sell a bike as a 27.5" bike, fit 26" wheels onto the S and XS sizes.

Have a look at Paul's Cycles, they specialise in brand new bikes from previous model years. They can often be a place for a bargain, but you may need to do some serious browsing.
https://www.paulscycles.co.uk/

bartimaeus

At 5'4" your lad is growing out of the 'kids' sizes but may be too small for some adult bikes depending on the range of sizes available e.g. Voodoo bikes start with a 16" frame for riders 5'5" which is worth checking as you might pick up a Hoodoo if you are a British Cycling member as I think they give a discount.

That said some manufacturers do XS 27.5 bikes which will definitely fit and if you check the manufacturers size guides I think you will find most listed as S (often around 15" or 38cm frames) are suitable for 5'4".

e.g. Vitus Nucleus: I know this range pretty well as I work for WiggleCRC and I also run a kid's MTB Club so this is here for sizing as these are slightly above your price range, sadly.

http://www.wiggle.co.uk/vitus-nucleus-2 ... 019-altus/ is the new kids 26er which will be too small

http://www.wiggle.co.uk/vitus-nucleus-2 ... bike-2019/ is the womens version which I think they should have just called 'compact' as Whyte do (see https://whyte.bike/products/604 ) which has an XS and an S - with the size guide saying S is for 5'2" to 5'6"

http://www.wiggle.co.uk/vitus-nucleus-2 ... bike-2019/ is the regular Nucleus which starts at size S which again says for 5'2" to 5'6" but is a bigger bike - this will likely be fine, but you might find the VRW is a better fit.

e.g.
Inside Leg goes from 67-76 on the VRW to 71-76 on the VR (so you can't get the seat as low, and have less standover)
ETT goes from 570 on the VRW to 600 on the VR with the Reach increasing from 386 to 420 (so it feels 34mm 'longer')
Wheelbase goes from 1102 to 1128
and your cranks go from 170mm to 175mm

So the good news is that at 5'4" you are in the Size S range for most manufacturers which gives you plenty of options. The bad news is that at £400 and an 'adult' bike you hit the light-strong-cheap dilemma in that most bikes are relatively heavy to make them well equipped, strong and 'cheap'.