Can anyone tell me where I can find frame geometry specs for my '72 Raleigh Grand Prix and other old Raleighs? I've tried Retro Raleighs and VeloBase - great sites, both of them, but nothing on this that I can find.
Probably not. Raleigh's heyday was a time when geometry charts were considered unnecessary for cheap bikes and proprietary for the expensive ones. Towards the end of the decade I believe the dealers had charts for the Pro models.
Let's travel back in time, before the Serotta fit system, before Dr. Andy Pruitt, before Body Geometry, before every mom-and-pop had to have a fitting system to be considered serious. College students simply bought the largest frame they could stand over. End of story.
This is what 1972 was like.
Elitest Murray Owner
Wouldn't it have something like 72 degree angles? That was pretty standard back then. Not really sure why you need to know.
You can measure the geometry yourself, with a tape measure and an angle finder, the magnetic type is good enough to get you started (~$10 or less at ACO). Seat tube is from the center of the BB axle to the center or the top of the seat tube, top tube is from the center of the seat tube to the center of the head tube, along the top tube center, chainstay just measure from BB center to the rear axle center.
The only thing that's tricky or finicky is to measure the fork offset. Here you have to line up a yardstick with teh fork centerline all the way to the ground, and hold it steady with one hand, or have a helper do that. Then with a small ruler measure the distance from the yardstick to the front axle center, perpendicular the the yardstick. You want the shortest distance. For this you should also measure to the millimeter or to 1/16 inch, since offset has a big influence on handling.
You can measure BB drop by measuring wheel axis height from the ground and BB axis height from the ground, and subtracting.
Why are you doing this? What are you trying to find out?
I'm reading a lot of technical stuff on this subject in Bicycle Quarterly, and I need the info to help me compare - on paper only, of course - my bike to others.
I have taken crude measurements of my Raleigh, and the figures I have are 47mm for trail and 75 degrees for the steering head, which seems steep.
"College students simply bought the largest frame they could stand over." Pegged me pretty good, dude.
Why do you want to just read that the bike you enjoy is terrible? Does not handle, and what you really need is a low trail French Rando' bike?
Originally Posted by hedgeapple
I really doubt the Grand Prix has a 75° head angle, unless it took a serious front end smack.
Elitest Murray Owner
I doubt it would be anything steeper than 73 degrees. I think you need to try measuring again.
Originally Posted by repechage
Why would I not want to do and be the best I can?
I like my Raleigh, I've had it since new, and I'm not gonna let it rot in the garage; but I'm also interested in the technical side of cycling, just as I am with motorcycling, engines, the farm, meteorology and just about anything else I've been involved with.
For what it's worth, I don't do brevets, though there's nothing to say I won't sometime in the future. If and when I do, I'll be on the Raleigh. What I am planning for the near future is a pukka touring bike with appropriate braze-ons and so forth. Since I like the Raleigh's character and wish not to change it, my only alternative is another bike. I can't test ride that which must be ordered, but I can sure do my homework, or at least try to.
I have a Rockhopper so I won't have to ride the Raleigh on our sand & gravel farm roads. Pickin' the tool for the job doesn't mean I've no use for others.
You might be surprised by what else is available. My complaint about nearly every Raleigh used to be "the bottom bracket's too high." Also, any new bike will have smaller 700c wheels instead of 27-inchers, which are becoming more and more difficult to find replacements for. But if you really want to know the dimensions of your bike then you'd do best to measure it yourself.
Originally Posted by hedgeapple;10027613 What I [U
For head and seat tube angles, I suggest taking a profile photograph of the bike. Use a tripod to make sure you're shooting straight on. Then take a protractor to an enlarged print.
My guess, though, is you're looking at 72 degrees parallel with about 1 7/8 inches of fork rake. If it's 25-inch frame, then the head angle is closer to 73.
I agree it's worth measuring the head angle again - I have found it takes a lot more care and sometimes trickery to get a good measurement. But if it's really 75, then it's 75.
Originally Posted by Mos6502
I think your reasons for wanting to measure your frame or know its geo are very good ones.
How did you measure the trail and the head angle?
Originally Posted by hedgeapple
Originally Posted by Road Fan
I used a 6' level (to find level floor), a couple of yards of string with a large nut tied to one end, a cheap plastic protractor that I've otherwise used to set up distributors, and a ruler that one of the pre-schoolers left on my school bus (I slipped it back into his backpack that afternoon).
Find level floor, plumb the bike vertical and prop it up, plumb the front axle and mark the floor, sight along the steering head with astigmatic, keratoconic, caffeine-lubed nearsighted eyeballs and mark the floor again, and measure the difference for trail. For head angle, I simply held the protractor to the steering head and plumbed the degrees. bbd, cs, wb, and other measurements are straightforward.
I like the photo idea. I have a friend who's an aircraft engineer, and I think he could do this with a digital camera and his computer. At any rate, I also doubt my 75 degrees but until I can come up with another verifiably more-accurate measurement, 75 is what I have to work with.
Most interesting bike at the moment is the Kogswell P/R - 64cm frame, choice of fork offset, fenders included. Surly's LHT is a likely possibility. Also waiting for coming framesets from Heron and Velo Orange.
Remeasured everything this morning, with care to eliminate parallax error: 686 tire/wheel diameter, 343 axle height, 59mm fork offset, 73 degree head angle, 41 trail. Plugged head angle, offset, and wheel diameter into Kogswell's frame geometry web-tool and got 43 for trail, so I think I'm close, or perhaps only sufficiently consistent in my errors to yield a valid result (??).
The bike is difficult to ride hands-off, and requires attention to hold a line. I know I'm too big for the bike (25.5" frame, with extended seat post and gooseneck) and that could effect things, but there's not much I can do about that. I think wider (32?) tires and lower pressures (currently 700-25c and 120psi) may help. I suppose I could keep the hands on the bars, too.