Refreshing

Hello! I have a Surly Karate Monkey Ops (old 29er version) with drop handlebars and I use it for EVERYTHING. I ride it every day to work (rain, sleet, or snow), I ride with a relatively fast paced weekend road group, I gravel race with it, and I plan to do my first double century on it:





My problem is that it has 72mm of trail with the 45mm tires that I have on it now. Wheelbase is 1071mm. If I lean into a corner the handlebars turn themselves and I feel like I am always fighting the bike. During the winter with my 2.5" tires it is even worse .


Using an online calculator if I swap out for 650b wheels with 42mm slicks the trail would drop to 66mm. This would fix a few things for me:


1. it would handle more nimble like a roadbike
2. I could fit my front rack over fenders and 650b studded tires
3. lighter wheels are faster


This frame was made for 29"x2.5" tires so I was worried about bottom bracket drop and pedal striking but the BB drop is 65mm and a few of the 650b rando bikes that I drool over have the same BB drop so it's gotta be safe right? I would love to buy a new frame but I just had a baby, sooooo, that isn't going to happen. But I have the hubs, and spokes for a 650b wheel build so I could do it for under $80. Am I understanding this correctly? A 29er+ with 650b slicks isn't going to murder me is it?

unterhausen

that swap should be ok

dsaul

65mm of BB drop is fine for that conversion. I'm currently building a gravel bike that required 650b wheels, to get around toe overlap and trail issues caused by the small frame size, and I chose to go with a 65mm drop.

base2 

Cheaper than a whole new wheelset, you might try skinny road tires. Without knowing all the relevent details of your bike in particular, yojimg shows with a 71 hta, 47 rake and 700c wheels the trail goes from 74 with 45's to 67 with skinny 23's. Obviously not cool for gravel, but for pavement use, a set of Nashbar cheapies even just a front one might suit the bulk of conditions? And a front only, leaving the larger diameter 45 in the rear would steepen the head tube angle for even less trail.

The length of the spokes arr determined by the hoop you get. So the ones you have *may* not work, depending. + tires, +tubes...$80 might not be the final cost.

That "push" necessary on the handlebars is why I don't ride Harley's. My Triumph had it too. It makes for a great cruising bike with high speed stability. They corner almost too good when you want them to and help you carry too much speed if the situation changes quickly. These bikes are better steered with your hips and are faster...if you are skilled enough to control it.

All the downhill bikes are getting greater and greater trail for this reason.

FBinNY 

As long as you've factored the drop in BB height, then you should be good to go.

IMO the issue of pedal strike is exaggerated for most people who tend to coast through hard turns, and should have enough smarts to keep the inside pedal up.

taras0000

Have you tried counter steering? I've found this to help on many twitchy geometries, bikes and motorcycles included

What is countersteering?

Streichy

Do ittttt

fietsbob

Yes ... BB drop , is from line thru axle centers

BB height/ pedal down clearance to the ground will be less by the reduced radius of the wheels you will install.

& because HTA line, and plumb line from axle crosses above the ground plane
you can also calculate how much shorter the trail will be.





.....

tuz

A 72 to 66 mm trail change sounds a bit small and I doubt it will have a noticeable effect. Seeing the amount of clearance on the fork you could try finding a shorter fork? That'll increase the HT (and ST) angles and have a stronger effect on the trail. At 1071 wheelbase a 30 mm shorter fork will increase the angles by ~1.5 deg.

WheelNut2

I second Tuz's suggestion. A shorter fork would really change the handling and might be a place where you can save some weight. If you get a fork with a bit more offset that will reduce your trail too. A new fork will realistically be a similar price to what you'd pay to build up that 650B wheelset. If all you have is hubs and spokes you'll still need tires, rims, rim tape, nipples, and valves. No way that is going to cost only $80. Tires alone will be at least $100 if you want anything half decent. Probably at least $200-300 for all those parts.

unterhausen

I suspect that the OP has made his decision sometime in the last 3 months