Rock Lobster frame sizing

scottalej

How do Rock Lobster measure their frame sizes, ctr bottom bracket to ctr top tube or ctr bottom bracket to top of seat tube?
I've just bought a 2007 Tig Team SL frame which was described as a 19" frame. It's 19" ctr bottom bracket to top of seat tube but only 17" ctr bottom bracket to ctr top tube. The top tube length also seems short for a 17" never mind a 19" at only 22" ctr head tube to ctr seat tube.
I'm 5'11" so I'm not sure this frame's big enough.

artillerydave

I've got a 18" Rock lobster B52 and I'm 6'2" and it fits like a glove, they are designed to be quite compact, tight handling frames that allow a lot of movement around the bike rather than a gatepost. Don't so much worry about what the tape measure says, ride it a see how it feels , I'm sure you won't be disapointed.

pdid

artillerydave wrote:

I've got a 18" Rock lobster B52 and I'm 6'2" and it fits like a glove, they are designed to be quite compact, tight handling frames that allow a lot of movement around the bike rather than a gatepost. Don't so much worry about what the tape measure says, ride it a see how it feels , I'm sure you won't be disapointed.

Agree, i`m 5'10 and got a 17" Team tig SL. Fits me perfectly and is great for chucking about.

scottalej

Emailed Merlin who confirmed that Rock Lobster frame sizes are measured ctr bottom bracket to top of seat tube

jamieayres

The top tubes on RLs are shorter than the norm, that is how i can swing riding an 17" but only be 5'7" as i have longer than average legs for me height.

scottalej

What length of stems are you guys using? I'd normaly go with a 90mm but may have to go longer to get a bit of stretch?
I have a Orange P7 for a hooligan hardtail so this will be the fast xc whippet to replace the donor Stumpy I've never liked.

artillerydave

on my B52 I run a thompson 4X stem at 90mm and 10% rise as stated this gives a great riding position on mine 18" frame at 6'2" however my frame is slightly different in that they don't make it any more and my geometry is for a 130mm-150mm fork not the 80mm-100mm yours will be set for.

tjm

I think it is pretty universal now to size MTB frames from the BB to the top of the seat tube rather than the centre of the top tube. Given the different design/position of the top tube I guess it makes sense.
However, I've been looking at this recently and found the most useful measurements are the standover and effective top tube length.
I've collected data on a few bikes and realised that on some bikes (eg Rock lobsters, Malts etc) I need a 19" frame to get reach I want whereas others (eg Trek, Fisher) I want a 17 or 17.5" to get the same reach. On the other hand, a 19" Fisher is too stretched for and in fact, as you have found, even on a 19" Rock Lobster I would need quite a long stem (and/or seat pushed back) to get the reach I am used to.

But, it depends on what you want from the bike. I found people taller than me who were happy with a standard Rock Lobster 19" .
In this discussion on sizes http://www.bikeradar.com/forums/viewtopic.php?t=12561143&start=15 the effective top tube length of a 19" Rock lobster is 23" or 584mm.
According to this link http://www.orangebikes.com/2006bikes/p7-pro.php the 17" P7 has an effective TT of 610mm.
So, if you want the same reach as your P7 then you need a stem that is 26mm longer than you have on your P7. Or of course move the seat back an 26mm, depending where you want the weight to go.
26mm might not sound like much but I moved the seat of a bike I had borrowed 15-20mm forward and it transformed the feel from uncomfortable to huge fun.
Don't take these sums as gospel. The seatpost is angled and the stem is angled so you can't directly translate a difference in effective top tube to the difference in cockpit reach but it hopefully gives you an idea of where to start.

btw. I tried a 17" P7 at the weekend. It felt very nice and comfortable. By coincidence the 610mm effective top tube length is very similar to my existing bike. I'm 5'10.5" with a 32" inside leg (trouser size).

I hope this makes sense!
Toby

scottalej

Thanks for that Toby.
My P7 is a 2007 17" which is ideal for chucking it around the woods but I'd probably choose a 19" for longer rides.
I'm going to build the 'Lobster up over the next few weeks.
The donor 2006 Stumpy is a 19" which isn't very responsive or chuckable despite some tweaks to try and sort it out.

jamieayres

scottalej wrote:

What length of stems are you guys using? I'd normaly go with a 90mm but may have to go longer to get a bit of stretch?
I have a Orange P7 for a hooligan hardtail so this will be the fast xc whippet to replace the donor Stumpy I've never liked.

I use a 90mm stem on mine, seems to be ok.