Dirt jump frame size

PB Forum :: Dirt Jumping & Street
Dirt jump frame size
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flag That-BikeGuy
Posted: Apr 5, 2019 at 14:11 Quote
Hey guys I wanna buy a dirt jump bike but I’m not sure what size I should get. I’m 5’10 and want to be able to flick it around in the air and truck it and stuff. I ride Xc and enduro and have been riding dirt jumps on my enduro bike which is a Rocky Mountain pipeline. So I can jump that but I want something that I can work on my dirt jump riding on and work on more progressive stuff and then use it as my dual slalom bike. Any help would be appreciated guys. Thanks so much!
flag cmc4130
Posted: Apr 5, 2019 at 18:58 Quote
That-BikeGuy wrote:
Hey guys I wanna buy a dirt jump bike but I’m not sure what size I should get. I’m 5’10 and want to be able to flick it around in the air and truck it and stuff. I ride Xc and enduro and have been riding dirt jumps on my enduro bike which is a Rocky Mountain pipeline. So I can jump that but I want something that I can work on my dirt jump riding on and work on more progressive stuff and then use it as my dual slalom bike. Any help would be appreciated guys. Thanks so much!

If you go back to one of the "classic" bikes in the genre (and I have one), the Black Market Mob is a good example of the size range.

https://www.pinkbike.com/product/blkmrkt-bikes/The-Mob/

Black Market measured the top tube the BMX way, which is the "actual" (not "effective") top tube, measured from center of head tube to center of seat tube. If you have frames with similar seat tube angles (in this case 71), then the actual top tube is a good way to compare. However, when you start comparing to bikes with very different seat tube angles, it's starts to be a less helpful measurement.

Some companies like TRANSITION have been publishing the "Reach" measurement, but not actual top tube. So, the Transition PBJ comes in Short and Long.
https://www.transitionbikes.com/Bikes_2019_PBJComplete.cfm

The thing is, though, because of the trend of Enduro bikes being "longer and slacker" I think it has caused some companies to make their DJ frames longer also. The Transition PBJ "Short" actually seems closer to the Large Black Market Mob. I could be wrong... but just going off a the PBJ's Short having a 23.6" effective top tube with a 72 head angle.... compared to the Mob's 22.5" actual top tube with a 71 head angle.

I'm 6'1" with long legs and I think the 22.5" Mob is well sized for me, coming from a BMX background. I also rode the 23"tt Transition Trail or Park a while back and it felt good also, but I definitely didn't feel like I needed it any longer than that. The 23" TOP felt big. Maybe someone coming off Enduro and XC bikes would want their DJ to feel similar...I don't know. But a long frame does not help with 360s, tailwhips, etc.

My Mob and Killswitch
photo

The Large (23"tt) Killswitch is significantly longer than the Mob because of the way the seat tube angle is different.
You can see here where I lined up the cranks/bottom bracket then compared the front end length. The 23"tt Killswitch was more than a half inch longer in the front than the 22.5"tt Mob.
photo
flag That-BikeGuy
Posted: Apr 6, 2019 at 5:29 Quote
cmc4130 wrote:
That-BikeGuy wrote:
Hey guys I wanna buy a dirt jump bike but I’m not sure what size I should get. I’m 5’10 and want to be able to flick it around in the air and truck it and stuff. I ride Xc and enduro and have been riding dirt jumps on my enduro bike which is a Rocky Mountain pipeline. So I can jump that but I want something that I can work on my dirt jump riding on and work on more progressive stuff and then use it as my dual slalom bike. Any help would be appreciated guys. Thanks so much!

If you go back to one of the "classic" bikes in the genre (and I have one), the Black Market Mob is a good example of the size range.

https://www.pinkbike.com/product/blkmrkt-bikes/The-Mob/

Black Market measured the top tube the BMX way, which is the "actual" (not "effective") top tube, measured from center of head tube to center of seat tube. If you have frames with similar seat tube angles (in this case 71), then the actual top tube is a good way to compare. However, when you start comparing to bikes with very different seat tube angles, it's starts to be a less helpful measurement.

Some companies like TRANSITION have been publishing the "Reach" measurement, but not actual top tube. So, the Transition PBJ comes in Short and Long.
https://www.transitionbikes.com/Bikes_2019_PBJComplete.cfm

The thing is, though, because of the trend of Enduro bikes being "longer and slacker" I think it has caused some companies to make their DJ frames longer also. The Transition PBJ "Short" actually seems closer to the Large Black Market Mob. I could be wrong... but just going off a the PBJ's Short having a 23.6" effective top tube with a 72 head angle.... compared to the Mob's 22.5" actual top tube with a 71 head angle.

I'm 6'1" with long legs and I think the 22.5" Mob is well sized for me, coming from a BMX background. I also rode the 23"tt Transition Trail or Park a while back and it felt good also, but I definitely didn't feel like I needed it any longer than that. The 23" TOP felt big. Maybe someone coming off Enduro and XC bikes would want their DJ to feel similar...I don't know. But a long frame does not help with 360s, tailwhips, etc.

My Mob and Killswitch
photo

The Large (23"tt) Killswitch is significantly longer than the Mob because of the way the seat tube angle is different.
You can see here where I lined up the cranks/bottom bracket then compared the front end length. The 23"tt Killswitch was more than a half inch longer in the front than the 22.5"tt Mob.
photo
Ok thanks so much. So would a 15 inch frame size specialized p slope be a decent size for me since I’m like 5’10 and looking for a bike I can throw around?
flag cmc4130
Posted: Apr 6, 2019 at 11:35 Quote
That-BikeGuy wrote:
cmc4130 wrote:
That-BikeGuy wrote:
Hey guys I wanna buy a dirt jump bike but I’m not sure what size I should get. I’m 5’10 and want to be able to flick it around in the air and truck it and stuff. I ride Xc and enduro and have been riding dirt jumps on my enduro bike which is a Rocky Mountain pipeline. So I can jump that but I want something that I can work on my dirt jump riding on and work on more progressive stuff and then use it as my dual slalom bike. Any help would be appreciated guys. Thanks so much!

If you go back to one of the "classic" bikes in the genre (and I have one), the Black Market Mob is a good example of the size range.

https://www.pinkbike.com/product/blkmrkt-bikes/The-Mob/

Black Market measured the top tube the BMX way, which is the "actual" (not "effective") top tube, measured from center of head tube to center of seat tube. If you have frames with similar seat tube angles (in this case 71), then the actual top tube is a good way to compare. However, when you start comparing to bikes with very different seat tube angles, it's starts to be a less helpful measurement.

Some companies like TRANSITION have been publishing the "Reach" measurement, but not actual top tube. So, the Transition PBJ comes in Short and Long.
https://www.transitionbikes.com/Bikes_2019_PBJComplete.cfm

The thing is, though, because of the trend of Enduro bikes being "longer and slacker" I think it has caused some companies to make their DJ frames longer also. The Transition PBJ "Short" actually seems closer to the Large Black Market Mob. I could be wrong... but just going off a the PBJ's Short having a 23.6" effective top tube with a 72 head angle.... compared to the Mob's 22.5" actual top tube with a 71 head angle.

I'm 6'1" with long legs and I think the 22.5" Mob is well sized for me, coming from a BMX background. I also rode the 23"tt Transition Trail or Park a while back and it felt good also, but I definitely didn't feel like I needed it any longer than that. The 23" TOP felt big. Maybe someone coming off Enduro and XC bikes would want their DJ to feel similar...I don't know. But a long frame does not help with 360s, tailwhips, etc.

My Mob and Killswitch
photo

The Large (23"tt) Killswitch is significantly longer than the Mob because of the way the seat tube angle is different.
You can see here where I lined up the cranks/bottom bracket then compared the front end length. The 23"tt Killswitch was more than a half inch longer in the front than the 22.5"tt Mob.
photo
Ok thanks so much. So would a 15 inch frame size specialized p slope be a decent size for me since I’m like 5’10 and looking for a bike I can throw around?

Dirt Jump and slopestyle bikes aren’t measured by seat tube length. In traditional MTB, a seat tube size of 15” would correspond with a shorter top tube and a longer seat tube (like 19”) would have a longer top tube. It doesn’t work that way with DJ frames. They all have low seat tubes for the low-seat position, then the sizes refer to how long the front end (and “reach”) is.
flag That-BikeGuy
Posted: Apr 7, 2019 at 7:46 Quote
Ok so a 15 inch reach is like from the seat to the bars or what?
flag cmc4130
Posted: Apr 7, 2019 at 18:56 Quote
That-BikeGuy wrote:
Ok so a 15 inch reach is like from the seat to the bars or what?

This is what “reach” means. It’s not actually that easy to measure it precisely...

photo
flag Aaronz25RS
Posted: Apr 9, 2019 at 3:10 Quote
NS Zircus, smaller, aluminum, light, LOVES to fly, loves to street, just feels good..
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