High safe cruising speed bike considerations/experiences

[RiverRat]

Howdy
I’m chasing some feedback in lieu of my next build this year regarding bike choice for maximum road/offroad safe commuting speed with good stability. Probably makes little difference but aiming to run the Tangent kit.

Obviously....? Downhill designed bikes seem to be the go so what atributes in frame design, measurements and angles would one be looking for for this kind of purpose?

Also some feedback would be great how you guys feel with your current and past setups when it comes to going fast comfortably or not.

Cheers

 

[John and Cecil]

Plus and fat tires seem to handle speed well, along with a decent full suspension setup. Larger framed bikes probably do better too, longer wheelbase usually helps with stability. We have a Raleigh full suspension bike with 27.5 x 2.8 tires and it feels well planted going down hills at 40mph - even with me and Cecil (my dog) and we weigh 215lbs between us. I would say the biggest issue at 40mph on our bike is the brakes.

 

[xnoitulos]

Plenty to discuss here, with many opinions. My 2 cents is this; Any modern DH geometry will perform great. One obvious barrier of course is frame design, particularly downtube shape. Unless you want to get fancy trying to tuck the drive inside the main triangle, possibly using custom motor mounts, best to find a traditional straight downtube design ("S" shaped downtubes have certainly increased in number). Aside from that, I wouldn't get too caught up in geometry numbers. Ideally, you'll want a slack headtube angle for stability, which practically all DH frames offer. [Only thing I've seen is dude put together a bunch of parts and frame with motor. Crashed very badly. Was using XC MTB frame designed for ~100mm travel fork, but installed non-suspension corrected rigid fork. Headtube angle was crazy steep and he lost the handlebar at speed ] What I think is most important is using quality parts. No Wal-Mart dually with bullshit suspension, brakes, hubs, frame, etc. Almost certainly should be running hydraulic brakes with 203mm front rotor, also requiring a fork designed for such setup. Rear hub should be something solid. I've been good with 3-4,000 watts on DT Swiss, Hadley, Mavic. Besides that, decent suspension goes a long way. Either air shocks that can be adjusted for the additional weight, or beefed up springs.

So, I have one bike setup for road with light spring (it's what I had) and lower fork pressure, really nice ride on streets, but would bottom crazy on real off-road. That's the Rocky Mountain Switch SL circa 2006 with Fox 36 and cyclone 3000w running stock 40amp controller and 72v 20s4p battery. Also have a Turner ? 7" Freeride with Totem fork running Lightning Rods Big Block 56amp controller, CA V3, 72v 20s6p battery. No speedo on the Switch/Cyclone but keeps up no problem with the Turner/LRBB. Turner can hit 42mph currently with 28t final drive (that's the one on the crank that drives the rear wheel iydk), hit 55mph with a 36t but it got bent during a chain drop :x Before this I had the LRBB on a Cannondale Perp with a 40t and hit 59mph (once, then hooked up 2 batts and 100amp controller and hit 59 again, only this time it took half the time to hit speed!) Cyclone is really quiet, not silent as hub, but still stealth. LRBB is pretty loud, so people will turn around when they hear the crazy whine of the #219 chains. Everyone will tell you something different, but limit speed to your own riding capabilities with the performance your equipment is providing. However, I don't think anyone would complain about only hitting 40mph. Good speed for getting around, moving with traffic. Also have old GNG gen2 on an 1997 Intense M1 with Bomber fork, old ass DT Hugi 240 hub which can take shifting under load 48v and 52v batts. Modded controller to get 35amps, modded primary reduction to use #25 instead of 15mm belt which would snap every 50miles or so. Nobody is going to be ready for my next project! which unfortunately I almost had done a year ago, but then TechShop went out of business so gotta hack it together now.

Cheers!

PS - Tangent kit looks tight!

 

[aCeMadMod]

if you want I meet up at World Cup track you can have test ride . with Dave gearbox 8)

only use 224mm brake rotors
bing your big boy pants
RiverRat

 

[motomech]

Most cities here in the States have bike lanes on the curbside of the road. Overall, city and Federal ordnances dictate a 20 mph limit, but the cops where I live won't bother one up to 25 mph. Riding above that speed becomes very dangerous, as cars think you are a normal bicycle and mis-judge your speed. The most common sort of accident involves cars wanting to make a right turn. They think they have time to get in frt. of you, slow down and make their turn, often cutting off the fast approaching bike. The other deadly scenaro involves car pulling out from side streets, once again, mis-judging the bike's approaching speed.
I would strongly suggest that if you plan to ride faster than 25 mph, you registar your bike for the street and wear motorcycle type safety gear.
If you ignore this warning, your claim to be concerned about safety rings hollow.