Frequently Asked Questions
General
What size frame should I buy?
We have a recommended sizing chart (shown below) to help point people in the right general direction. If you happen to land near the upper or lower limit of the size range you should use your best judgment when deciding your frame size. You can also contact us for a suggestion.
| XS | S | M | L | XL | XXL |
| 4'8" - 5'2" | 5'1" - 5'6" | 5'5" - 5'10" | 5'9" - 6'1" | 6'0" - 6'4" | 6'4" - 6'8" |
Generally speaking, larger frames give better high-speed stability and a calmer feeling ride. Smaller frames give better maneuverability at lower speeds and a more playful feeling ride.
Why high-pivot with an idler?
Through testing we found the high-pivot design to be able to achieve the most positive ride characteristics we were looking for out of any design.
By allowing the rear wheel to move up and back (more in the direction of the bump impact) it not only helps the bike feel smoother in the rough, but also to carry speed better in the rough. This is because the wheel tends to “hang-up” less on sharper, more square-edged bumps and therefore gives the rider a smoother and more controlled ride.
The idler pulley is necessary on high-pivot designs to keep chain growth and pedal kickback to a minimum, but it also allows us to more carefully tune pedaling performance through anti-squat. The Contra MC was able to have the same percentage of anti-squat at sag (where you pedal most) in every gear. This is something that is difficult to achieve with a traditional (non high-pivot/ non idler pulley bike).
The Contra MC also uses a much larger than normal 24-tooth idler pulley which increases efficiency by reducing friction and wear compared to smaller idler pulleys.
What is your warranty?
Lifetime. Every Contra frame comes with a lifetime warranty against manufacturing defects.
Do you ship internationally?
We do!
Each frame shipped internationally will see increased shipping costs as well as taxes, duties, and custom's fees, but it can be done.
Do you offer sponsorships?
Currently we are unable to offer any sponsorships.
Frame
Where are your frames actually made?
Contra Bikes are made in the USA.
The frames are mitered, fixtured, welded, and powder coated all in Santa Cruz County. The majority of the machined parts are made in Capitola, California by Mather Machining. The pivot hardware, pivot housings, cable guides, head tubes, and bottom brackets are made by Paragon Machine Works in Richmond, California. And the chainguides are made in Hood River, Oregon by Hans at Motor Control Technology.
Why are your frames made out of steel?
There are a few reasons…first is steel’s superior fatigue strength. Basically it means that below a certain level of stress (known as the fatigue limit or fatigue strength) the steel parts of the frame can last a lifetime without failure. In reality not all stresses are below the fatigue limit of the material, but it does lead to a tremendously long lifespan of the frame and is part of why we offer a lifetime warranty.
Secondly, 4130 steel is a great material to work with since there is the ability to shape and manipulate tubing without requiring annealing followed by heat treatment of the tubing.
Third, it is stiff in a more compact package. This helps mostly with the swingarm where you need good stiffness, but a low profile to allow for good tire, chainring, and crank clearance.
Lastly, during this time of supply chain issues it is easier to source quality options in material from multiple sources.
Can I mount a water bottle to my frame?
Absolutely!
There are a pair of water bottle bosses with bolts on the top side of the downtube. Combined with your favorite water bottle cage all frame sizes fit a large (26oz/750ml) water bottle inside the front triangle.
Can I get internal cable routing?
Not at this time.
If we do this in the future…the only way we want to do it is with a well engineered guide tube system inside the frame. One where you push your cable housing or hydraulic hose in one end and it pops out the other side perfect every time.
Can I purchase my frame without the EXT rear shock?
You can, but currently we feel the EXT is the highest performance option for this frame. We’ve tested other shocks and none of them perform as well as the custom tuned EXT Storia Lok V3 shock that we spec.
Can I get custom geometry?
Yes!
We can do +/- 10mm of reach for any given frame size. This helps for riders between sizes.
We can also do a custom seat tube length for taller or shorter riders.
We also offer a mixed wheel version and custom chainstay lengths if desired.
Contact us about your
Component
What type of headset do I need?
Any headset that has a 44mm ZS (Zerostack) upper combined with a 44mm EC (External Cup) lower to fit a 1-⅛” to 1.5” tapered steerer. A few compatible options are listed below.
Cane Creek 110 ZS44/28.6 H8 | EC44/40 - Complete BAA0762K
Cane Creek Hellbender 70 ZS44/28.6 H8 | EC44/40 - Complete - Black - BAA1187K
Chris King Inset7 (says EC34/EC44 on Google, but is actually a ZS44 upper EC44 lower)
Wolf Tooth Performance Upper Headset Cup “Zero Stack” ZS44/28.6 6mm Stack combined with Wolf Tooth Performance Lower Headset “External Cup” EC44/40
White Industries “ZS44/EC44” Headset
Hope “2” Upper Headset “ZS44/28.6” combined with Hope “H” Lower Headset “EC44/40”
What size seatpost do I need?
31.6mm diameter dropper posts with “Stealth” routing.
The seat tube lengths are on the shorter side to allow riders the ability to run long travel dropper posts. Recommended starting points are listed below, but this all depends on the desired saddle height and frame size chosen.
XS: 160-185mm travel
S: 160-185mm travel
M: 185-213mm travel
L: 185-213+mm travel
XL and XXL: 213+mm travel
What size is the seat clamp?
35mm diameter. The frame comes with a Bike Yoke Squeezy bolt-on seat clamp that is very light and clamps extremely well.
What is the rear hub size?
148mm “Boost” with a 12mm thru-axle
What rear axle do you use?
Burgtec for Santa Cruz 173.7mm rear axle, 12mm diameter, Thread: M12 x 1.0mm pitch
What derailleur hanger do I need?
SRAM Universal Derailleur Hanger (AC-DRHG-MTB-A1)
Machined aluminum versions of this hanger such as the Wheels Manufacturing Derailleur Hanger (404-02) and North Shore Billet SRAM UDH Derailleur Hanger (NSB DH0152) will also work on this frame.
What is the largest rear disc brake rotor I can use?
223mm diameter 2.3mm thick rotors are the maximum size that will fit.
What is the smallest rear disc brake rotor I can use?
203mm diameter. The direct post mount eliminates the adapter usually required for 203mm rotors. We feel that the increased braking power and heat dissipation from larger rotors better matches the intended use of the bike.
Rear Suspension
What is the recommended sag setting on the rear shock?
28-32% of rear shock travel is what we’ve found to be the sweet spot in testing. This equates to 18-21mm measured at the rear shock.
How do I remove/install my rear shock?
There are a few different ways to most easily remove your rear shock from the Contra MC.
COIL SHOCK REMOVAL
On a coil shock the easiest way we have found to remove the shock is to first record your spring preload and rebound settings. Once these are written down turn your rebound dial fully slow (clockwise) then back off the spring preload on your coil shock all the way as far as it goes (towards reservoir end of the shock). Make sure your climb switch is set to the open position.
Once this is done, compress the back end of your bike by pushing down on the seat with your hand until the spring once again rests on the preload collar. It should look like your bike is almost bottomed out. Now remove both shock bolts and carefully remove your rear shock in its compressed state from the non-drive side of the bike.
COIL SHOCK INSTALL
To install the shock we recommend setting the rebound fully closed, fully backing out the spring preload collar to the max, setting your climb switch to the open position, and compressing the shock until the coil spring has contacted the preload collar. Your shock should look almost bottomed out. Then carefully feed the shock into the frame from the non-drive side of the bike. Mounting the shock in this compressed state allows increased clearance to fit it into the frame.
Align the holes in the shock reducers with the shock bolt holes in the frame and install and torque each shock bolt. Once installed, turn your rebound dial back to your recorded setting and reset your spring preload collar so the shock is in its extended and normal state.
AIR SHOCK REMOVAL
On an air shock the easiest way we have found to remove the shock is to first record your air pressure settings and make sure your climb switch is set to the open position. Once this is done attach a shock pump to your rear shock, compress the back end of your bike by pushing down on the seat with your hand, and use the bleed feature on your shock pump to let air out of your shock rapidly. This allows the negative air pressure to “suck down” the rear shock into a compressed state. It should look like your bike is almost bottomed out. You can now remove the shock bolts and carefully remove your rear shock from the non-drive side of the bike.
AIR SHOCK INSTALL
To install the shock make sure it is in the same compressed state that is achieved from following the recommended removal instructions. Once your rear shock is in a compressed state carefully feed the shock into the frame from the non-drive side of the bike. Mounting the shock in this compressed state allows increased clearance to fit it into the frame. Align the holes in the shock reducers with the shock bolt holes in the frame and install and torque each shock bolt.Once installed, inflate your rear shock to your recorded setting so the shock is in its extended and normal state.
What size shock hardware does the MC use?
20mm width x 8mm diameter hole upper (on the reservoir side/top of the shock where it mounts to the top tube) and 30mm width x 8mm diameter hole lower (on the non-reservoir side/bottom of the shock where it mounts to the lower link)
We strongly recommend running a bearing style lower shock mount where it attaches to the lower link since this link sees a bit of rotation. This helps reduce friction in the suspension and increase small-bump performance.
Some options are:
RWC Shock Needle Bearing Kit, 30.00mm (NBKRWC30)
Fox Roller Bearing Kit (812-06-096-KIT)
RockShox Eyelet Bearing Bracket and Bolts (Only for bearing compatible Deluxe/Super Deluxe rear shocks) (11.4118.049.000)
I want to run a different shock than what comes stock, what do I need to know?
The MC uses a 230 x 65mm stroke metric shock.
Mounting hardware is 20mm width x 8mm diameter hole upper (on the reservoir side/top of the shock where it mounts to the top tube) and 30mm width x 8mm diameter hole lower (on the non-reservoir side/bottom of the shock where it mounts to the lower link).
Fox, Marzocchi, RockShox, MRP, Cane Creek, DVO, BOS, Manitou, Fast, and SR Suntour rear shocks are suspected to fit, but not all options have been checked for fit yet.
The current PUSH Industries ELEVENSIX rear shock does not fit because of the sideways reservoir orientation.
Ohlins and Formula rear shocks are both suspected to not fit due to the potential for the reservoir to contact the underside of the top tube.
Contra Bikes is not liable for any damages due to shock fit issues if you choose to purchase or install a shock that does not fit.
Can I use an air shock?
Yes.
The leverage ratio has roughly 24% progression. We’ve found that to be enough to run an air shock without having to pack it full of volume reducing spacers.
Fork
What fork do you recommend?
XS: 160mm travel 27.5” fork with 37mm offset
S: 160mm travel 29” fork with 44mm offset
M-XXL 170mm travel 29” fork with 44mm offset
Offset can be changed if you prefer a different steering or handling feel. Really anywhere between 36-58mm.
Of course you can also experiment with a longer travel fork (all the way up to a 203mm travel dual crown) or shorter travel fork if you desire. Keep in mind that going outside the recommended fork travel will affect the geometry and handling of the bike.
Can I run a different offset fork?
Yes.
Offset can be changed if you prefer a different steering or handling feel. Really anywhere between 36-58mm
Stock offset is 37mm on 27.5” forks and 44mm on 29” forks.
Can I run a dual crown fork?
Yes.
200-203mm travel (or less) downhill forks can be used such as the RockShox Boxxer, Fox 40, Ohlins DH38, Manitou Dorado, DVO Onyx Dual Crown. The fork bumpers must be installed properly on the stanchions to prevent metal on metal contact of the stanchions with the frame when turned.
We also highly recommend running these forks with a “Zerostack” lower headset cup for 1-1/8” steerer tubes. This helps to offset the longer axle to crown from a longer travel fork in order to minimize the geometry change compared to a single crown. This is because the stack height of this lower cup is 8-9mm less than the external bottom cup required for a tapered steerer tube single crown fork..
For comparison: a 203mm travel Fox 40 ran with a Zerostack lower cup will ride roughly at the same height and head angle as running a 180mm travel Fox 38 with an EC (External Cup) headset. So more travel for the same ride height, which we think is cool!
Crank and Bottom Bracket
What bottom bracket do I need?
73mm English threaded
What size cranks should I run?
This is entirely up to you, we like 170mm cranks, but 165-155mm cranks are also a great option for more pedal clearance.
Can I run a different chainline than 52mm boost?
Yes.
We make 52mm and 55mm chainline options, but they must be paired with the same chainline cranks. This ensures that the chainline running from the front chainring to idler is aligned.
The bike is not designed to clear a narrower chainline than 52mm.
The stock 52mm chainline works well with most drivetrain and crank options.
The 55mm chainline was designed specificallyfor SRAM Eagle Transmission and comes with a T-Type idler pulley.
Chainring and Chain
What is the maximum chainring size I can use?
34 tooth
What length chain do I need for my bike?
This depends on the size of the frame, front chainring diameter, and drivetrain you are running. Most frames will require an extra piece of chain between 6 to 16 links longer than a standard 126 link chain and the installation of two master links to attach it. This is an unfortunate side-effect of having a high-pivot bike with such a forward idler.
With that said…Shimano does sell “E-bike” versions of SLX, XT and XTR 12-speed chains that are extra long with 138 links. These chains will generally work on XS-L frame sizes and XL-XXL frame sizes if they are running smaller cassettes (such as the 10-45 Shimano). On the XL and XXL frame sizes the longer chainstays will require two master links and a longer chain than the 138 link “E-bike” chain (in most cases).
KMC also sells 136 link “E-bike” 12-speed chains which should work on XS-M frames and possibly some L frames depending on cassette and front chainring size.
We have a small selection of Shimano 12-speed 138-link “E-bike” chains available for purchase with your final payment. When they are gone they’re gone.
Chainguide
Can I run my bike without the lower chainguide?
No.
The lower chainguide is necessary for a number of reasons.
First, to make sure there is enough chain wrap engaging the front chainring.
Second, to keep the chain on the front chainring through the rough.
And third, to minimize derailleur cage movement from excess lower chain growth. This has the added benefit of increasing small bump sensitivity since you don’t have to overcome the derailleur clutch’s resistance when compressing the suspension.
Can I run my bike without the upper chainguide?
No.
It is necessary to help keep the chain on the idler.
Why is there a 3D printed chainguide mounted to the seatstay and do I have to use it?
The 3D printed chainguide is there to keep the chain from deflecting into the rear tire tread and subsequently getting pulled down and jammed between the chainstay and rear tire.
It is not recommended to run the frame without this upper guide installed.
Wheel and Tire
What size wheels do I need for my frame?
XS: 27.5” front and rear
Small: 27.5” rear, 29” front
Medium-XXL 29” front and rear
What is the maximum tire width that I can use?
This depends on the brand and tire model. We designed the MC with plenty of clearance around 2.5” wide tires (roughly 12mm all the way around). 2.5” is the maximum recommended width, but most 2.6” wide tires will fit as well (just with reduced clearance).
Can I convert my 29" wheeled frame to a mixed-wheel setup?
Yes.
You can run a 27.5” rear wheel on the stock 29” wheel frame, but it will drop the bottom bracket height considerably (12mm or so) and will slack out the head and seat tube angles by around 0.8°.
You can also request your frame to be built mixed-wheel specific after your order has been placed. This maintains the same BB height, head angle and seat tube angle as the stock geometry chart. This also repositions the idler pulley mount to maintain the desired anti-squat and pedaling characteristics.
Maintenance
What bearings are used in the pivots?
Enduro 3802 Double-Row “MAX-type” bearings. These are 7mm wide with a 15mm inner diameter and 24mm outer diameter.
There are eight of these bearings total per frame, four in the upper link and four in the lower link.
Do you sell a bearing removal/installation tool?
Not in our store, but Real World Cycling makes bearing removal and installation tools that fit.
The full set of tools cost around $120 + tax and shipping. The list of required tools including part numbers is listed below:
(1) PIVOT BEARING CUP FOR 24MM OD BEARING SBT-24-OD
(1) 15MM ID PIVOT BEARING EXTRACTION PILOT SBT-15-ID
(1) SUSPENSION BEARING GUIDE 6802 SBG-6802
(1) RWC HANDLE SET FOR MODULAR BEARING TOOLS 8MM-HANDLE-SET-RWC
What are the torque values for all the bolts on the frame?
Upper and Lower Shock Bolts: 16Nm
Upper and Lower Link Bolts: 20Nm
Idler Carrier Bolt: 9Nm
Idler Pulley Bolt: 20Nm
Upper Chainguide Single MRP Bolt: 1.2-1.3Nm
Upper Chainguide Mounting Bolts: 5Nm
ISCG Mounting Bolts: 8-9Nm
Rear Axle: 12-15Nm
SRAM UDH Bolt: 25Nm
Seat Clamp: 4.5Nm
Can I buy a spare idler pulley?
Yes.
Once bikes are shipping spare idler pulleys will be available in our store.