Gravel bikes are some of, if not the most versatile bikes on the market. Fast and efficient enough for a road century, capable enough to tackle cross country mtb routes and muddy bridleways, and as you would expect fast and comfortable on gravel tracks and fire roads. The ultimate go anywhere bike, some would say.
In an effort to maximise this versatility many will decide to run two wheelsets. This makes a lot of sense as most framesets now accommodate different wheel sizes with a wide range of the many tyre sizes available.
So, what’s the ultimate double wheelset setup? What are the advantages and the drawbacks of the many combinations available. I cannot answer these questions for you, as there are just two many variables and personal preference will play a large part. What I can do though is pull together some technical information, add in some personal experience and top it off with some recommendations.
Why would I want multiple wheelsets?
Where places like the US have a well established gravel riding scene, here in the UK we are still exploring this relatively new (in its current guise) format of riding. It holds true that products like tyres and wheels developed for the US market will not necessarily suit the demands and variety of the riding in the UK as it often involves slogging through deep mud and rocky bridleways, grassy fields or canal towpaths.
Each ride is different and if you can optimize your bike for each route with a simple swap of wheels then …..
Search for The Holy Grail
My current bike is a Genesis Fugio, with 650b wheels and 50mm Donelly Xplor MSO tyres. Its a great bike, it`ll plow through anything and goes downhill faster than a Swiss bobsleigh team. But all that comes at a price, weight. The stock wheel/tyre combination is capable of generating its own gravitational field!
So the hunt for an upgrade started, literally, at Hunt.
The plan was to convert the stock 650b`s to tubeless to shed some of the weight. Then get an additional Mason X Hunt 700c wheelset with a light fast rolling tyre to help cover bigger distance rides and events. The 650b set would be a burlier, monster cross type setup for an extra plush ride quality on shorter and rougher rides where the extra weight would be less of a burden.
One lightweight/fast rolling minimal tread 700c set and one 650b big volume set with bigger tread. Sounds perfect, right?
Before I tell you about my journey towards this wheel and tyre nirvana, we should consider a few technical details. Changes in wheel and tyre size will obviously alter the overall circumference of the wheel. This has knock on effects for axle height, gear inches, trail geometry and bottom bracket height. Here are some good links to other articles which explain this in more detail than I am prepared to go into right here.
Tyre Size and Volume.
The relationship between tyre size and volume is well explained here
An example, the jump from a 31mm tyre to a 38mm will return a 50% increase in volume.
Bottom Bracket Height, Gear Inches and Trail Geometry.
This would take a whole post on its own so here is a link to another blog that has done a good job of explaining these and also has further info about wheel size choices.
The Struggle is Real
The first job was to see if I could get the current Donelly Xplor setup tubeless on the stock Fugio wheelset.
After three hours, punctuated by three separate trips to the LBS for rim tape, then a tubeless pump, and finally some different valves I had to admit defeat and refit the tubes, it was the February edition of the UKGBC Forest of Dean group ride the next day and I needed the bike.
This part of the plan was put on hold while I sorted the other wheelset out as the results might influence the type of tyre I wanted for this wheelset.
I ordered a set of Mason X Hunt 4 Season 700c wheels, and a pair of Bontrager GR2 Team Issue tyres. A light wheelset (1571g) and light (440g), supple 120tpi, fairly large volume tyre with a little tread but not too much. Perfect! Or so I thought.
Setting these tyres up tubeless was a breeze, the bead seated straight away and they held pressure. After fitting the wheels into the frame the clearance at the chain stay bridge was less than ideal at approx. 2mm.
After a quick tarmac test ride that gap closed to leave the tyre rubbing on the chainstay. I contacted Genesis who confirmed that the frame should have clearance for 40mm tyres and gave the stock answer of “every tyre mounts up differently depending on rim width.”
Frustrated by the lack of success so far and not having a chance to really test out these tyres on gravel I went back to the drawing board.
If 40mm wont fit the frame what do I do? Try 38mm? Maybe, but having already spent £80 on a set of tyres that didn’t fit I wasn’t keen to repeat the experience.
Play it safe I thought and drop to a 36 ish.
Several hours of internet research later and I settled on Kenda Flintridge 35mm, which apparently will blow up to more like 37mm, perfect i thought, again.
Actually I think the fitting of the GR2`s may have done me a favour. Going back to the 650b wheelset and looking for a tyre set to fit tubeless led me to the WTB Resolute 42mm. Not as big a volume as I wanted but tyre choice for this wheel format is still quite limited. If the GR2`s had fitted I would of been left with two wheelsets with practically the same volume tyres fitted, where’s the versatility in that? I thought.
The Resolutes arrived just in time for the March UKGBC Forest of Dean ride, and so I found myself once again, trying to setup tubeless tyres less than 24 hours before the ride, what could go wrong?
These were much harder to get seated than the GR2`s but after giving them a 160psi “shot” 4 or 5 times from my tubeless track pump they eventually popped into place. The first thing I noticed about these tyres is how the knobs aren’t as big as they look on the internet.
Weighing up before and after, this simple tyre swap and switch to tubeless had shaved a whopping 850g from the wheelset! That is huge and will definitely be felt out on the bike. A very successful upgrade so far, but how will they perform?
650b Test Ride.
Today was the March edition of the UKGBC Forest of Dean group ride and the first test for the Resolutes.
Overnight they had held up well with only a small amount of air loss from the front. I loaded the car up and set off to the Canop Cycle Centre. The forecast was not looking good, heavy rain and high winds all day long. I wondered if anyone else would be mad enough to turn up.
After grabbing a coffee on arrival I spotted Ian as I exited the café. I should of had more faith, Ian loves a mad forest ride as much as I do and believe me we have already had some mad rides here! We were joined by one more crazy local to make up a group of three.
We headed off into the forest on one of the main fire roads which climbs up and away from the carpark. Within 15 minutes my front tyre was almost flat, so a quick stop to top up the air gave a welcome breather. Ten minutes riding later, and it was almost flat again. I told the guys I would try one more top up and if it went flat again I was going to bail (a good excuse to get out of the persistent rain). Unfortunately, the tyre held up for the rest of the ride, and I had no excuse for an early bath.
The volume of the Resolute at 42mm is a lot smaller than the 50mm they replaced but the comfort levels from the more supple, lighter tyre were indistinguishable. My worries of not maximizing the volume on the 650b set were put aside.
Grip is excellent on hard and loose over hard gravel and even surprisingly good in mud, but the limits of the tyre can be found easily here if you are not careful.
The small knobs and almost continuous centre tread mean they don’t drag on tarmac as much as you might expect and the supple casing means they roll well on rougher surfaces. Early days but an excellent start.
To be continued…………