[weevie]

Before I do the angles calc on a Sat night (gee life after kids is wild..) has anyone done this or got a link to a basic geo calc web page? As I build it next month I’m thinking of adding a 1-2 degree works angleset on my lads new old stock build before I put it all together from the rolling stock bits I bought. I believe it’s 68 deg (?) at moment with the xfusion 80mm fork so a degree or two (or 1.5) should effectively steepen seat tube a tiny bit, drop the bb and sort the front for more downs (we only have steep up and down where I live) . Also if the 80mm fork dies by time child mk2 gets on it or turns out to be a bit rubbish then I could prob get away with a junit 100mm fork (with a little more sag perhaps..) .
P.s if anyone has a copy of the old geometry table could you please post it below? Looking for seat tube angle and bb drop in case I have to screw my long discarded maths head back on … I can measure the rest but life is short..

 

[svinyard]

I wouldn't worry too much about the geo changes. It'll be fine and a lot better regardless of what you do. The BB might drop a bit but it's not going to be a ton and it'll be worth it. Often the 1.5-2d angle sets also include and external cup that adds some stack and will counter any BB drop anyways. Regardless, it's a nice enhancement and turns the bike into a more capable trail bike.

Our experience with a 20" yama jama was that the steep HTA led to OTB's for sure with that XC style geometry. Under sag and chunder, that 68d turns into 69d too....then boink, the kid shoots over. My DJ has a 69d HTA and its not confidence inspiring lol.

When we switched to a JUnit fork, it slacked out the bike an our OTB's immediately disappeared, even on park days. Part of that is the stock fork was divey once the kid started to slay. The other part is that the new fork had more travel/longer A2C and hence slacked the bike out.

I spoke with Prevelo a while ago and they said they updated to more modern trail geometry for the same reasons.

 

[weevie]

Yeah I have one on my carbon tall boy ltc. That frame was lovely in the shop on a work trip to Orange County years ago so I bought it. Turned out the seat tube was waaaay long and the head angle way too steep even when I put 150 pikes on it.. I should move on really but I’m loathe to swop it as it’s hardly used as I got into XC racing to stay fit for climbing which was my thing and it sat in the attic dripping with nice stuff (for 2013…) Until my kids can out run me I’m keeping it….
I’m going to add one to the kids bike .. just not sure which to get at moment as I’m not with the bike at present so don’t know the cup sizes. From google photos it looks both are integrated cups so it may be the diameter is wide enough to keep both internal even with 1.5-2.0 degs.

 

[wallander]

Go for it! I did convert our Spawn YJ 20” a while back. Worked out real good. See a report I did here: Reducing HTA on Yama Jama 20"?

 

[weevie]

Hej… thanks for that. We have the YJ 20 as the current ride and haven’t bothered with changing that. My kid uses it mostly now on the pump track and so it will be a hand me down to his bro next summer. Will do the 24” though. BTW Swedish ? or at least live there? I’m English but my family all Swedish. May move back sometime but we’ll see … noted snowed in Lulea this weekend already! Time for my family-in-law to dump the bikes for skis in just a few weeks.

 

[wallander]

Yes, I’m a Swede in Sweden! And my relatives live in Luleå. A skislope 2h away from them (close to the polar circle) has already opened, amazing!

Kåbdalis säsongsöppning startar den svenska skidsäsongen

På söndagen öppnade Kåbdalis sin första skidbacke för säsongen. Öppningen av backen blev den första i Sverige för skidsäsongen 21/22. ”Tidigare år har vi blivit omsprungna av Idre fjäll men vi har lärt oss mycket om hur man sparar snö”, säger Johan Gunnarstedt, ägare av Kåbdalis skidanläggning.

www.svt.se

 

[weevie]

Wow! Good to get there before the imminent 23hr darkness! My wife grew up on skis at bygdsiljum. Tiny place but now a v. small bike park in summer as well. When I win the lottery I’ll buy a large chalet in Are for the kids to do both In the meantime they’ll have to make do like normal people…

 

[rton20s]

Seems like you have you answer. But, I have found this site to be a helpful tool when researching fork and headset angle changes.

https://bikegeo.muha.cc/

 

[weevie]

Thanks. Good link. I’m ready to order but I don’t know the internal diameter of the head tubes until back home in a while …upper internal zs49? 44 ? lower 49? 56? etc

 

[weevie]

I wouldn't worry too much about the geo changes. It'll be fine and a lot better regardless of what you do. The BB might drop a bit but it's not going to be a ton and it'll be worth it. Often the 1.5-2d angle sets also include and external cup that adds some stack and will counter any BB drop anyways. Regardless, it's a nice enhancement and turns the bike into a more capable trail bike.

Our experience with a 20" yama jama was that the steep HTA led to OTB's for sure with that XC style geometry. Under sag and chunder, that 68d turns into 69d too....then boink, the kid shoots over. My DJ has a 69d HTA and its not confidence inspiring lol.

When we switched to a JUnit fork, it slacked out the bike an our OTB's immediately disappeared, even on park days. Part of that is the stock fork was divey once the kid started to slay. The other part is that the new fork had more travel/longer A2C and hence slacked the bike out.

I spoke with Prevelo a while ago and they said they updated to more modern trail geometry for the same reasons.

Hi. Did you just buy a generic booster adapter for the front wheel? I’ve just sprung for a 100mm J unit 24” and likely will build from scratch with an Angleset over Xmas - but don’t want new wheels. Frame currently at the powder coaters to make into a less flashy/stealth ride
The 24” Rokkusuta deal fell through - so will stick with a hard tail until boy can back flip (joke) - but enough is enough and don’t want to buy new wheels as well.
Recommendations for a generic wheel kits to get to 110mm?

 

[svinyard]

I just used this. Another dude on here used it as well.

Amazon.com

Hi. Did you just buy a generic booster adapter for the front wheel? I’ve just sprung for a 100mm J unit 24” and likely will build from scratch with an Angleset over Xmas - but don’t want new wheels. Frame currently at the powder coaters to make into a less flashy/stealth ride
The 24” Rokkusuta deal fell through - so will stick with a hard tail until boy can back flip (joke) - but enough is enough and don’t want to buy new wheels as well.
Recommendations for a generic wheel kits to get to 110mm?

 

[weevie]

Almost a month since I’ve given this any thought but back to it. Kinda. Generic wheel spacer sorted from X Zoom. Frame still at powder coaters due to their backlog and my new DM 145mm crank just came with one arm measuring 140mm dooh! Anyhoo ….For those vaguely interested (not even me I suspect) the just now measured a-c on the 80mm x fusion fork supplied with mk1 YJ 24 is 461mm. The new 100mm Junit is 455mm. Going to send the 100mm fork back and have ordered already the 120mm version and a WC -1 deg. Should thus get extra 40mm travel plus the changes all add up to 2 deg (66 ish) changed HT angle, with no material BB rise or change to ST angle.

Seems this bike will prob end up costing me same as a stock nukeproof/discounted Com. Meta 24 … but at least will have better components, look better, and for the moment gives me a distraction from dealing with the ramifications of our PM adding most of the random countries I work in to the ‘COVID no easy travel’ Omicron RedList. The x fusion forks will be saved and travel adjusted to 120mm when I can be bothered and mounted on a NS Clash 14” 26” frame seen on CRC (but bought from their eBay outlet shop for 70% retail). Ideal for a preteen hardtail hack for Xc/town/pump track/riding away from the police, as applicable, depending on how he turns out…

 

[weevie]

This could be the slowest build ever known to man (or woman) but no rush. Now home in UK, its pretty cold and wet for a kid to do more an hour or two's rding and he fits perfectly on the 20" still as he is big enough to heave it around so all good.
As such this prob wont get a run out until Easter/Summer (just as well as wont be finished...) but thought Id prove I dont come on MTBR to post made up bike stories and they are actually true (as well as dull) So, we have (drum roll pls) ...actual (glacial) progress.
Frame now back from PC'ers - matt RAL window grey for £50 to evict the Spawn pink car crash colour.. Mocked up the rolling stock as per photo to check set up with the now installed 1 deg angleset plus the 120mm MJt forks in place. All aligns perfectly for what should be much better ride downhill at circa 66 HT with almost no change to ST/SOver..
I still have only one crank arm .. the replacemwent for the missing 145mm must be lost in the Atlantic , also I need to add some small personal decals, install all the regular stuff etc.
Have also swapped the 40mm Spawn boat anchour stem for a 2/3 weight cheap but good 35mm. Have some new deore brakes, new slx shifter with neon green cable, an XT 11sp mech. Added an old Kore cut down seat post and SDG Fly Jr saddle. Still need to buy a 11-42 cassette when get round to it and an 11 speed chain. A 26T blackspire installed on the (1/2) crank for the v steep hills here

La de dah... enough wittering... have a good xmas for those that do and holidays season for anyone else ... Ill bore you futher in 2022 when I get round to finsihing it ..

 

[svinyard]

Bro...that's sick. I love it. You fixed the geometry with that angleset too. Is the stock 24" Spawn yama jama have a tapered headtube?

A couple of notes:
1- set the fork sag up properly...don't follow the PSI chart. Maybe a click or two of compression at most. When you air up that sweet fork, make SURE you screw on the pump firmly (there is a second internal valve that has to be depressed or it won't air up the neg chamber and sucks in the fork...no big deal tho). If you pump doesn't do it, get a different pump.
2- Those tires are great and light, but we found that they just get SHREDDED on any sort of chunky terrain (unless they are the DH versions perhaps). We've only run DHF/DHR2 since then and those are bad ass.
3- Pedals...I found that Commencals Ride pedals are pretty damn good and a near perfect size (don't get the tiny tiny ones as those are more for 5-7yro feet). Only like 40$ for nice metal pedals. They've held up to some wild abuse for us.
4- You should throw on a dropper from KS. Its a sweet build, might as well make it proper . KS Lev Integra is super nice and works ultra well for the kids low weight with very, very easy lever push as well. Air it down to like 100psi and it'll be sweet. Dropper posts are a godsend for kids. Both my kids have them now. When installing the internal routing, you'll need to pull the Bottom Bracket drive side and the cup. Run the cable and then install the cup back in (super tight fit but whatever it works). Get the post slammed and installed all the way before installing the cup.
5- If you want to go full crazy, there's no other brake like the Dominions with the kids lever (SFL - small finger lever). They are ridiculously nice (one of the best brakes ever made imo) and amazing ergonomics for the kids hands.

 

[weevie]

Thank you
-Yes standard tapered - needed an external top though for the andleset -ec44/zc56. - so just .5cm spacer on top not to ground the stem. Bottom milling was just enough to take the bottom cup. Must have been microns… the inner depth on the supplied headset was shallower.
-Thanks re fork settings. Helpful
-tyres yes- they will die where we live. Not groomed trails… but will get the tubes out and see how we go
-Dropper - agree. My lad is young so it’s not needed yet but will add in all likelihood when stock easy to get.
—brakes sound nice but I’ll resist. 2 pot Deore are lying around unused and he weighs nothing so should be fine. Due to the trails here there is a risk his ability will be slowed by being on a hard tail when he is 9/10 years so if that’s the case I’ll need the ££ for that money pit. Also need to buy some decent pads so best do that first
Yet another crank arm on the way from the US. May get it rideable one day ..

 

[weevie]

And relax….
I had a couple of hours this afternoon whilst home to get it done. Just needs a chain and the tubes out and my lad to grow about 5cm … oh and to be home enough to ride it in earnest. All good …his brother can kill it off in due course if boy mk 1 doesn’t.
El cheapo eBay pedals at moment as his feet to small for the Spank Spoons -will switch them when he rides it properly. ThoJo sticker decal just their names split and joined. Cost £1- for kiddy gifting impact only.. will flake off before long. (Update…. And …they’ve been taken off and stuck on the dog…)

 

[weevie]

Set up and equalised fork chambers but even with my weight/use not getting more than 90mm of the 120mm ‘as sold’. Wasn’t expecting 120mm .. but 25% less seems a little off…Prior users have a view?