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Oh Wise Singletrack Hivemind,
Please tell me what you reckon!
I’m 6’7” with a 6’10” armspan. I’m toying with the idea of ordering a custom Marino dirt jumper, more or less copying the geometry of a X-Long Transition PBJ, but with a long enough seat tube that I can plop a 450mm seatpost and saddle in it in order to ride sat down decent distances to pump tracks/riding spots etc. [then swap in a short post and saddle at the spots if it won’t go down all the way] My comfy riding saddle height is 850mm, so I think a 450mm seat tube would just about do it.
I know that would mean a fair bit longer seat tube than is traditional for a dirt jumper, so higher saddle and top tube than normal…. But I’m only planning on riding pump tracks and very mellow trail type jumps….but it seems cool to be able to ride on it across town (Sheffield) to places without needing a car. Plus as above I’m massive so don’t suppose I’ll particularly notice. AND it’s an option to have a dropped top tube with seat tube/top tube gusset to drop the top tube a bit. I guess it’ll end up sort of halfway between a dirt jumper, a 26” hardcore hardtail/klunker/pub bike kind of thing.
The Transition X-long frame has 465mm reach with 400mm chainstays. It’s big/long for a dirt jumper but I figured something of those dimensions would be a bit more chill to ride than my current ‘long’ Dartmoor 26Player that just seems tiny and scary…when I bunnyhop the bars barely clear my knees (and I have 75mm rise bars on it)….and I’m WAY off the back of it before the front wheel lifts as me arms are so blinkin’ long. I'm learning how to jump at the mo and feel more confident on my normal hardtail tbh.
Does the above seem stupid? As ever, any thoughts/insights/suggestions much appreciated, thanks!
I reckon it'll be fine. It's only an extra 100mm on the seat tube, so nothing too drastic. If you're a big lad you'll have the leg clearance anyway.
Before getting something completely custom though, I'd have a quick snoop around on Geometry Geeks and compare a load of older 26" frames to the PBJ. I think it'll be the reach that you'll struggle to find, mind.
What’s your normal hardtail? I’d have a look at the geometry of that and have a think about how much smaller you’re likely to be comfortable with.
Any idea what size bikes pro DJ/slope riders your height ride?
The armchair engineer in me wonders if the chainstay length should be a bit longer so it's in proportion to your height? I know it's a DJ / pumptrack type bike but unless you are doing flippy whippies or whatever, you won't really benefit from having such short stays IMHO. Given that you are going fully custom, it's something worth looking into.
Thinking about the seat tube angle, I guess you're pretty heavy given your height. With the angle being 72deg, 400mm of post on is going to shift back 12cm from the top of the seat tube. The total 850mm tube+post is going to be 26cm behind the BB, and so 14cm in front of the rear axle (given 400mm chainstay). Also it's a 27.2 post, no idea about strength of the tube/post at such length and weight.
Maybe thing about scaling the whole thing up not just the seat tube?
How are you going to carry the short seatpost and saddle around with you, or store the long set while you're doing the jumps? I guess you're way out of range for a dropper, even the 240mm ones.
A DJ is single speed and geared correctly will spin out at a lower speed than you want it to. Just get used to doing a little spring then sitting down and chilling for a bit.
Your comfy riding height on a DJ bike should be way lower than a normal trail bike imo.
6'3 here, ride a 13" DJ bike, never have the saddle anywhere other than slanmed
In response to the thoughts above (thanks everyone)...
- old hardtails and checking geometry geeks is a good shout.
- my usual hardtail is a Pace 529 XL (510mm reach) which is comfy but I reckon I could definitely go smaller by a decent chunk for a messing about bike. I don't know what very tall BMX/slopestyle riders do...Kelly McGarry was a big 'un wasn't he?... I do know they're all a shed load braver and better on bikes than me so I guess they just hunch over and deal with it!
- yeah deffo no flippy whippies!... aim is to go up in the air and come down in a fashion I somewhat expected with a minimum of swearing..so yup longer chainstay would probably feel more predictable.
- and yes! weight/leverage is a consideration for sure when stickin a big post up... I'm 85kg, not too crazy but no featherweight either. Guess if it's custom could make sure seat angle isn't going to cause permanent wheelies, and could spec a chunkier seat tube diameter.
Not sure I'll do it...but it's tempting and it seems fun to make something versatile, that's not really on the market.
-
and 5lab, I know I should just sprint and cruise... but I've one pump track that's 3 miles away and 500ft climb...another one 5 miles, and the legendary Bolehills are 4 miles and 600ft up... seems neat if I could you know pedal/climb normally and chill to get to these fun places...then swap seat and have it slammed for hopping about and whatever.
Maybe I should learn to love the Dartmoor parts bin special I made...but I really really dwarf it and even just hopping it seems weird...like I can't pull bars in to where I want as they seem so low on my legs when I pop up...but could just be my bad technique.
Do you 'need' a perfect saddle height on a pump track bike? Plenty of people ride all over Sheffield on BMX's. You just stand up more and ride slower.
I have a PBJ (in Sheffield) and the saddle never moves. It's just not that kind of bike.
I have a Marino hardtail (probably very similar in geometry to your Pace) and have toyed with the idea of getting a slightly longer than normal jump bike made. I'm 6'5" so a little shorter than you and I have a BMC 4x bike which I love but it feels tiny compared to a modern bike with much longer reach. My idea was to make a 650b hardtail with reach of around 470mm, at your height you could still have a reasonable length seat tube and it not get in the way. My thoughts behind going 650b is you can use more modern parts and the 1" increase in wheel size shouldn't affect people as tall as us, it's a bit like how 22" wheel BMX is now more popular.
This thread reminded me of a couple of bikes.
You could ask 18 Bikes in Hope if they would do you a version of this...
www.cotic.co.uk/news/2020/coticdirtjump
Sonder do a custom Ti frame option, so you could request something like this...
alpkit.com/blogs/news/sonder-custom-titanium-dirt-jump-bike
Personally I wouldn't be obsessing over saddle height. I'd make sure you get enough reach and stack height so that you aren't bent double while you're riding it. Could you not track down a regular X-long PBJ to see how you get on with it before you go full custom?
A mate of mine (also in Sheff as it happens) did something very similar with a BMX and the incredibly long seat tube from a folding bike.
Worked a treat, I reckon you'll be fine.
APF
I can't help thinking you would better with something like a medium sized hardcore hardtail. A Bfe or Nukeproof Scout in 27.5" wheels and single speed conversion.
With the right fork and tyres you could tick all the boxes
Personally I think that building a giant jump bike because you’re a giant is a great idea. People would do the exact opposite if they were super short. Might be worth also thinking about also raising the bars as well and running wider than the average jumper (unless your planning to bar spin and tail whip.
Paul Aston of Aston MTB is a lanky chap (maybe not as tall as you thought) and built himself a custom pump/jump bike as he felt off the shelf ones were too small for him.
Here’s the link, I think he explains his geometry, spec and the reasons behind them.
Also Marino are probably a good choice as you can save money by not paying extra for the fancy tube sets. A few guys I’ve spoken to aren’t even sure if they got them when they paid for them anyway, while others are very happy with their frames.
I’d love to see the finished product when you get it.
Once again really helpful thoughts everyone, thanks again.
I suppose no I don't need need perfect saddle height for pedalling...and I'm aware getting close to it will compromise pump track and jump riding....but my knees are 44 years old, and being able to zip somewhere fast, in comfort, then dick about mildly on pumps/jumps seems fun. Those custom Cotics/Sonders do look nice...but custom UK-made 853/titanium is going to be £££$$$$$$!
I could try getting a Transition PBJ, but RRP is like £600+ and Marino custom all in will be a fair bit cheaper, even with delivery and import taxes.
@zerocool I hadn't seen the Paul Aston bike, that's excellent! what he calls the 'Old Man Dirt Jump bike'. He says 470mm reach, with "I think 440"mm chainstays. In the video though he doesn't seem too sure on the second number. They don't look quite that long hmmm maybe I'll email him. Here's the more detailed video of that bike:
and folding bike seatpost...that's a great idea...holy moly you can get 600mm ones ha ha probably best not to boing around too much sat on that.
I have the junky parts for a 26 build so still thinking 26. Just looked at the Cotic site and it says February will be their LAST batch of BFe 27.5s!!! No way! I guess that's another thread.
Buy this as a stand in for the Marino so you can start riding and decide what you need. Then sell it to me.
@sharkattack yeah good plan! I did see that on Pinkbike and was tempted. Riding a bunch more definitely is a good idea. I do have my 26Player parts-bin special (not quite as long as the 'Long' Transition) and a big 29er hardtail to ride so I reckon I can bounce around on them and figure out what ideal proportions are for a custom middle-aged dirt jumper (for a 2m person).
We should have an old mans, stiff back, grey haired jump club. Meet at Charnock or something and talk crap, case landings, have a go on each others bikes etc.
I can't wait until it's a bit lighter, I reckon I could get to Hillsborough pump track in 10 minutes from work. Maybe double that to Bolehills.
(not quite as long as the ‘Long’ Transition)
Nothing is, that's why I bought mine originally. When I needed another one (insurance replacement) the XL was available but I bottled it in case it was too weird. I'd still like to ride one. I considered buying that one from Rotherham so I could do a DIY paintjob without wrecking my currently mint frame. Then I'd use whichever one looked better and sell the other.
I can’t wait until it’s a bit lighter, I reckon I could get to Hillsborough pump track in 10 minutes from work. Maybe double that to Bolehills.
You probably live near me.
I ride through Hillsborough Park on the way to work, and just after the pump track opened last autumn (actually before it opened, but after the builders' fence got torn down) I thought - I'll have some of that.
I pretty much immediately slid out on a berm (did I mention I was riding my Pompino 😀 ) and made a right bloody mess of my knee. And I had a pair of cream chinos to wear at work that day, d'oh...
I live in Heeley but I work in the city centre. And yes, I know what bloody knees and shins feel like so any riding will be strictly after work!
If you go for it use a large seat post diameter, don't go for a standard 27.2.
Don't aim to get your saddle at full seat height, except that you will be cranking out the seat but have it high enough to relax every once in a while.
I wouldn't go with longer chain stays but a longer top tube than standard.
I don’t know what very tall BMX/slopestyle riders do
Mike Hoder is 6'4" so tall but significantly shorter than you. He rides a normal BMX all be it a long one with high bar and taller head tube.
Telescopic seatpost (not dropper)?
Like the classic Titec Knockscoper (or whatever it was called)?
I reckon you can get away with a fairly long seat tube as at 6’7 I’m guessing your inside leg measurement is pretty long (either that or you have the proportions of a cartoon gorilla!).
I think the Marino is the way to go. I’m only 5’11 and 44 (nearly) and I still find traditional jump bikes uncomfortable. And you’d probably be fine with 26” wheels for what you want, maybe 27.5 if you want to future proof yourself.
My kids are 4 and I find my 29er HT a bit too fast for pootling along with them at the moment and not great on pump tracks (where they spend most of their days) so will probably build up a single speed jump bike as well. If I have the cash I might we’ll go Marino just to add some comfort.
@sharkattack I'd be well up for a bit of middle-aged solidarity figuring how to case things better this year. I'm just down road in Meersbrook...how did you know I talk crap, have grey hair and a stiff back though? Well spooky. I also have a bunch of dumb little kicker ramps and bunnyhop bars I built to amuse the kids and to make bumps in the wood a bit perkier so that could be fun too...may have to figure out a bike that's not going to kill me straight away first. I would go for it with what I've got but I'm not so sure that's wise!
I know what you mean about the XL Transition possibly being weird...I'd worry about that too. Still very short back end (400) with fairly big reach (465). That's not a good combo on my 29er for me as I feel all weight's on back wheel and my body weight can't pump front through feet much at all. Weird one... @TheBrick says don't go longer on the chainstays even if you do stretch the front...and I guess Transition more or less agrees with him.... but I can't think straight... if I had say 420mm chainstays you'd think that's mental on a DJ bike, but scale that down from my size to someone who's say 5'10" and it's like them on 372, which is well short. I know it's more complicated than that... maybe short as possible is always best for such a machine and it's the small sizes that are compromised with having to fit a wheel in??? The above mentioned Paul Aston is in favour of lengthening the back tho, hmmmmmm.
That Matt Hoder chap does all sorts of nutty stuff with his BMX seat half up, ha.
And oh yeah @TheBrick that's a good shout on the saddle height, just high enough to sit down and cruise every once in a while without me knees around my head would probably do it.
@finbar your bloody chinos story is very touching, thanks for sharing.