A roadie with no idea on mtb sizing (adult and 12/13 yr old)

bianchi_dave

Hi All

Long tome roadie (25yrs) and this is my first visit to the 'dark' side of the forum so go easy!
I'm needing new hardtail mtbs for myself and my son and not sure what sizes we need. I only have one LBS with very limited stock.

First my son - he is 12 years old and currently about 155cm in height. He rides a Frog 62 (with 24") wheels but is now maxed out on the seatpost and stem spacers, in fact he's quite aero on it!

Anyhow, I'm torn between the next size up Frog 78 (26" wheels) or an XS adult bike. I should add that he is severely autistic and struggles to understand gearing (amongst most other things) so 1x is preferable, which the Frog has. It seems you have to spend a bit more before adult bikes come equipped with 1x, but at least they have front suspension, which the Frog lacks. An adult bike would also be more future proof as I'm sure he'll be sprouting shortly (his mother and grandad are tall).

Budget for son's bike would be around £400 to £700 ish.

Secondly me - I'm about 5'10" (177cm) and generally ride 54 cm road frames (Scott and Trek). My old Specialized mtb is 19" frame so I think I'm between S and M in most brands.

I'm happy to spend £1000 - 1500. Ideally I'd also want 1x and looking at bikes with SRAM Eagle 12sp and the like. Ideally I'd want carbon as I do quite fancy doing some gnarly uphill trails. At this price range carbon bikes seem to be about 1 to 1.5 kg lighter?

Buying online as there's lots of deals out there just now, and want to make sure we get the right sizes first time round.

Anyone have any thoughts?

Cheers

The Rookie

For your son I wold look for a 27.5 in an XS or S, will be a little too big at first but he'll get more use out of it at the right size. Ref 1x you can always use the limit screws to lock out the front mech over the middle ring, won't have a wide range but if he's not tackling steep hills that would be fine.

For you, yes it sounds like you're between an S and an M and which is better may well be brand dependant, the key measure is effective top tube length and thus reach, so maybe measure your current bike (and working out if slightly longer or shorter is better) and compare to whatever you look at. As for carbon, well yes it's nice but at that price point some carbon bikes end up heavier than aluminium frames due to using cheaper and heavier other components.

This ticks a lot of boxes as a potential for your son, 1x11 using Deore and decent enough quality Judy fork. Pinnacle is Evans' in house brand and I believe still made for them by Merida (the worlds second largest bike manufacturer).
https://www.evanscycles.com/brand/pinnacle/kapur-3-2022-mountain-bike-709366#colcode=70936611

For you, how about this, super lightweight carbon XC bike.
https://www.chainreactioncycles.com/vitus-rapide-29-crs-mountain-bike/rp-prod206934
Again Vitus is CRCs in house brand and they are were you get the best deals, a similar spec from a mainstream brad would cost about £500-750 more.
My FS 29er is 12.8KG with a dropper post, many mid range hardtails weigh more!

As for weights, always look at independent reviews, manufacturer weights cannot be relied upon as there is no 'standard' for how to weigh them, OK for comparing bikes from the same manufacturer, not different ones!

bianchi_dave

Thanks Rookie, that's helpful. In road bikes I typically look for effective top tube of around 540mm, but not sure how this transfers to mtb sizing due to the shorter stem and more upright position. Going by my height, M looks to be the more appropriate size though on most manufacturers websites. A few of the bikes also come with a dropper post fitted.
I quite the look of the Cube Reaction TM. Start fitness have it for around 1k but only size S left. 2022 model also reduced elsewhere, to around 1400 🤔

bianchi_dave

oxoman said:

Just spotted this in an email flyer. Might be worth asking / googling for info and reviews etc.
https://www.planetx.co.uk/i/q/CBOOWHGX/on-one-whippet-sram-gx-mountain-bike#CBOOWHGX

Thanks, will have a look

bianchi_dave

I'd also consider used for myself, as I do all my own spannering so no issues there. Unlike road bikes, most mtbs will have taken a fair bit of punishment though....

singleton

I'll share my experience over the past 12 months or so.
I was riding roadies for about 10 years and I got my first hardtail "tractor" about a year ago. My road bikes were Cannondale and Specialized 56cm frames and I'm about 6 foot tall.

Frame geometry on a MTB is important based on your intended use.

When I just want to ride on a canal towpath or easy trail then a smaller frame with steeper angles will work really well. An XC bike.
But as soon as I start to ride some more difficult and technical trails etc, then a longer and slacker geometry with a bit more room to move my weight around is really helpful - especially if you descending over.muddy and slippery roots in the depths of winter. A trail bike.

I bought a trail 29er as I thought it might be more flexible for my first MTB. It's maybe a little slower on the quicker stuff, but much easier for me to ride on the harder stuff.

bianchi_dave

singleton said:

I'll share my experience over the past 12 months or so.
I was riding roadies for about 10 years and I got my first hardtail "tractor" about a year ago. My road bikes were Cannondale and Specialized 56cm frames and I'm about 6 foot tall.

Frame geometry on a MTB is important based on your intended use.

When I just want to ride on a canal towpath or easy trail then a smaller frame with steeper angles will work really well. An XC bike.
But as soon as I start to ride some more difficult and technical trails etc, then a longer and slacker geometry with a bit more room to move my weight around is really helpful - especially if you descending over.muddy and slippery roots in the depths of winter. A trail bike.

I bought a trail 29er as I thought it might be more flexible for my first MTB. It's maybe a little slower on the quicker stuff, but much easier for me to ride on the harder stuff.

Sounds very similar to my intended use. Most of the time it will just be cycle path and the local woodland trails which are easy going, but I'd like the option of taking it up into the hills. I'm in Scotland with a few decent hill trails not too far away. My son wouldn't manage that though, unfortunately.

So based on you riding 56cm road frames, I guess you went for a large mtb?

singleton

Yes correct.
Supply and choice were limited when I got mine last Autumn, but I found a lightly used Merida big trail 500 on eBay in size Large.

The Rookie

oxoman said:

Just spotted this in an email flyer. Might be worth asking / googling for info and reviews etc.
https://www.planetx.co.uk/i/q/CBOOWHGX/on-one-whippet-sram-gx-mountain-bike#CBOOWHGX

Nearly linked to that but its heavier and less well equipped than the Vitus once you add the £250 for the suspension fork.

bianchi_dave

This looks to be a great deal on a Whyte 901 v4?
https://ukbikesdepot.com/m15b188s864p41276/Mountain_Bikes/Hardtail_Mountain_Bikes/WHYTE_901_V4_2022/RS_GB/160396?gclid=CjwKCAjwp9qZBhBkEiwAsYFsb-9hfyTAWQLMCxTfp_hbihm927sD-OonHrBM4BFV8sOZtyHf-1JAARoC2Y4QAvD_BwE

singleton

Yes I’d agree that’s a great deal.
It’s aluminium (& 27.5” wheels) so not the carbon that you first stated you were looking for, but a few mates have them and love them.

bianchi_dave

singleton said:

Yes I’d agree that’s a great deal.
It’s aluminium (& 27.5” wheels) so not the carbon that you first stated you were looking for, but a few mates have them and love them.

Seems decently light though, which is the main thing. And it's my size. I see the 900 series is marketed as a more hard-core or enduro hardtail but I guess that makes no difference to my intended use?

singleton

It should be great and I’d buy it.

Optimal geometry for going uphill is a bit different from optimal geometry for going downhill, but most bikes are a compromise.

I found that the tyres made a MASSIVE difference to how mine felt.

The Rookie

bianchi_dave said:

Seems decently light though, which is the main thing. And it's my size. I see the 900 series is marketed as a more hard-core or enduro hardtail but I guess that makes no difference to my intended use?

It weighs the same (12.8Kg) as my 29er Full suspension!

The Vitus I linked to is about 20% lighter.

The 27.5 tyres won't roll quite as well as 29er wheels, the slacker head angle will mean its not as nice on steeper climbs and the high front end will mean a less racy riding position.

bianchi_dave

The Rookie said:

bianchi_dave said:

Seems decently light though, which is the main thing. And it's my size. I see the 900 series is marketed as a more hard-core or enduro hardtail but I guess that makes no difference to my intended use?

It weighs the same (12.8Kg) as my 29er Full suspension!

The Vitus I linked to is about 20% lighter.

The 27.5 tyres won't roll quite as well as 29er wheels, the slacker head angle will mean its not as nice on steeper climbs and the high front end will mean a less racy riding position.

I managed to get a look at the 901 yesterday, albeit in size S and thought it was a bit of a tank.

I guess that will be the case with most bikes though, when I'm used to my sub 7kg Addict RC.

I also like to ride narrow handlebars (38cm) on my road bikes and the bars on the 901 felt like the old 'cow horns' I remember from the 80s!

Starting to wonder if mtb's are my thing, might just keep riding the old one until it dies....

singleton

MTBs are heavier than road bikes or even gravel bikes - even a 29er trail tyre can weigh 1kg alone - 2kg just for tyres.

If you want a lighter bike and narrower bars then you might want to look at some XC bikes - they will be both of those things.

singleton

As @The Rookie suggested - if you can find something like this:
https://www.chainreactioncycles.com/vitus-rapide-29-crs-mountain-bike/rp-prod206934
It could be good - a claimed 9.4kg and with fast tyres and narrow bars.

The Rookie

bianchi_dave said:

The Rookie said:

bianchi_dave said:

Seems decently light though, which is the main thing. And it's my size. I see the 900 series is marketed as a more hard-core or enduro hardtail but I guess that makes no difference to my intended use?

It weighs the same (12.8Kg) as my 29er Full suspension!

I managed to get a look at the 901 yesterday, albeit in size S and thought it was a bit of a tank.

I guess that will be the case with most bikes though, when I'm used to my sub 7kg Addict RC.

I also like to ride narrow handlebars (38cm) on my road bikes and the bars on the 901 felt like the old 'cow horns' I remember from the 80s!

Starting to wonder if mtb's are my thing, might just keep riding the old one until it dies....

The 901 is a hard hitting trail bike, what you describe you want is a lithe XC bike and that fits in with the Vitus I linked to or similar. Trail bikes will have wider bars than an XC bike to suite the usage, however bars can be cut down (can't do that with drops!)

Yes it will weigh more, a decent 29er tyre is going to be about 650g, more than double the weight of a road tyre, wheels have to be stronger and hence heavier, also the suspension forks will be about 1500g plus compared to about 450-500g for a decent road bike one. Drivetrain will be similar weight overall (heavier bits offset by the 1x saving), bars and stem a little lighter.

My old 26er HT was 9.5Kg and my 26" XC full suspension was 9.8Kg. 29er adds about 1.2-4kg over 26" (mostly for the wheels and tyres - at this price point) but off road they faster roll over rough ground easily makes up for it in overall cross country pace (which is why all the racers use 29).

Have a look for a faster XC bike and see how you feel with that, doesn't have to be the Vitus (you won't find one in a store) but a similar 'enough' one to get a feel for it, most big brands will have a similar bike (at probably around £2500!). For example, this from Decathlon https://www.decathlon.co.uk/p/29-carbon-mountain-bike-xc-900/_/R-p-300807?mc=8643985

But yes, it will always feel heavier riding than a sub 7kg roadie! I don't have a road bike but my road biased hybrid commuter (PX London Road) is sub 9kg and obviously feels flightier than my 29er full suspension (when it hasn't got the 4.5kg of pannier on it I commute with anyway!).

singleton

There are a few other carbon xc bikes to consider around your price point:
https://www.paulscycles.co.uk/bikes/mountain-bikes/cube-reaction-c62-one-hardtail-mountain-bike-2022-redwhite__8899
https://www.teamcycles.com/bikes/mountain-bikes/2022-trek-procaliber-95-xc-lithium-grey-and-trek-black__18698
But as with road bikes, at this price point a lot of your budget is going on the frame if you buy carbon. A good ally xc bike may not be that much heavier than a carbon bike.